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Android · offline data collection · version 1.5.2
A phone that works
as a real instrument.
Signal Collector continuously records the sensor, radio and network data your phone can reach, straight into the phone — no cloud storage, no measured data leaving the device.
Real captures · Pixel 10a
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A running measurement. The ring shows satellites, networks and sensors as they arrive.
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Choosing what to measure. Every source is a row that says what it records.
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Start, reset and stop, with the duration, distance and record count above them.
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The bottom of the panel: what each source is doing and the file that leaves the phone.
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Settings: delivery to your own server, units, and what happens after stopping.
Internal test
The next version, before the Store has it.
Every build lands in the internal test before it goes to production. Join with the Google account the phone is signed in with and the update then arrives like any other.
MVP scope
One run.
The whole context.
- 01GPS, GNSS and device sensors
- 02Cellular networks: LTE / 5G / 3G / 2G
- 03Wi‑Fi, Bluetooth and network context
- 04Continuous internet mapping over Wi‑Fi and cellular
What it is for
Every case ends
in a file.
A measuring instrument is not sold by its list of sources but by the question it answers. Six of the twelve situations the app was built for — each one a walk, and a file at the end of it.
The dead spot in the meeting room
Walk the floor with the phone in your pocket and say a note at every door. Out comes throughput second by second, the AP the phone was really on, and a room instead of an argument between two departments.
A drive test without the van
Both SIMs scanning, GPS at one second, the phone locked on the dashboard. Every change of technology, Cell ID or PCI lands as an event, so handovers come out located to the metre.
A survey where GPS gives nothing
In a warehouse the sky is a roof. Mark each aisle with a photo from the app's own viewfinder and collect APs, MLO links and RTT distances — a coverage map before the first new AP is bought.
Sensors that report on their own
Dozens of BLE thermometers around a building, none of them paired. Walk past and their temperature, humidity and battery voltage arrive named and in SI units, beside the bytes they came from.
Proof for the landlord
Ten minutes of walking gives a file with a timestamp, a position, signal strength and photographs of the rooms. “The signal is fine everywhere” becomes a claim that can be checked.
A customer who will not have a cloud
Measure as usual and deliver to your own S3, WebDAV or SFTP — or hand over a file. Photos and voice notes never touch the phone gallery, so the NDA stays signable.
Work you can
watch.
Version 1.5.1 ships all twelve languages in every install, lets you see a long export or Reset at work, and adds a loose notebook for points, photos and tests taken without a running measurement.
Languages that are actually there
Google Play used to deliver only the languages the phone had at install time, so the per-app language choice offered Czech and the others with no strings behind them. All twelve translations now ship in every install.
A comet on the key
Download, Share and Reset take seconds to minutes on a large measurement. A comet now runs around the edge of the key, the tail growing with the finished part, and a live line under it says how much is done, how long it has run and roughly how long is left. Free space shows before the write starts — amber when tight, red when the export would not fit.
A loose notebook
Survey points, photos, voice notes, the one-off internet test and a Wi-Fi throughput cycle no longer need Start. Without a running measurement they go into a separate record with no collectors, no wake lock and no charge against the free hour — with its own card, its own Share file and its own Clear.
Share from the icon, system controls
Long-press the app icon once a measurement has stopped and Share is there next to Start; it opens the app and starts the export straight away. Switches, text fields, choices and messages are now standard Android controls — the keys and the instrument stay as they were.
Nothing lost
on the way out.
Version 1.5.0 adds no new key. It goes over everything that could cost a measurement its data — a Reset under a stray thumb, a point number used twice, an export torn in half by a second export — and closes each one, with a test that keeps it closed.
A Reset that asks first
The first touch on Reset deletes nothing. It opens a dialog that names what would go: the measurements, the photos and the voice notes. Cancel keeps everything; only a confirmation wipes. A thumb that brushes the key in a corridor no longer ends a day's work.
Points keep their numbers
Stop a measurement, start it again, mark a point: it gets the next number, not a repeat of one already in the file. The same holds for photo and voice marks, so two records never share one point index and the export stays unambiguous.
An export in one piece
Export takes a single atomic snapshot of the database, and two export requests at once queue instead of tearing one archive. The manifest is computed from the bytes that actually went into the archive, with a SHA-256 for every file. You get a readable archive or a plain error — never a silent torso.
Failures that stay failures
When the writer loses a batch, Stop cannot turn the run into a success. Encrypted Eddystone telemetry stops showing up as plausible plain numbers. Dual-SIM attribution, WPA3-only networks, probe time budgets and the microphone handoff are hardened, and the expandable cards tell TalkBack what they are.
Started without
opening it.
Version 1.4.0 puts Start and Stop where the hand already is — the quick settings shade and the app icon — and lets a marked point carry a photo and a voice, so what a corridor looked like leaves together with the numbers.
A tile in the shade
Start and Stop in the quick settings shade, within reach from any app and over the lock screen, where a widget cannot go. Over a secured lock it unlocks first — what it starts is location with a microphone. It measures with whatever the app measured with last, so one key never starts two different measurements.
Shortcuts under the icon
A long press on the app icon is the only control that is always on the home screen, so it offers the one thing that makes sense now: Start while nothing runs, Stop and Mark point once it does. The gate the launcher walks through is locked with a token no other app can read.
A photo and a voice at the point
A marked point can carry a photo taken through the app's own viewfinder, or a spoken note of up to ten minutes. The media never touch the phone gallery: they sit in the app's private storage and leave only through an export, which becomes a single tar.gz with a SHA-256 for every file.
Settings you can take with you
A new phone set up like the old one, without walking through two dozen sources by hand. Passwords go into the backup only if you ask, and only after a fingerprint, a face or the screen lock. The licence and the free hour never travel in it.
The data, open
to be looked at.
Version 1.3.0 puts the keys on the home screen, opens the measured rows inside the app, lets the controls be carried to the edge of the display, and starts reading sensors that are not in the phone at all.
Keys on the home screen
Three widgets that need no app opened first: a point mark with your own labels, a key that starts a saved set of sources, and a tile showing what one source is collecting. Each key keeps its own copy of what it starts, so a preset switched in the app later changes nothing on the home screen.
Rows you can read on the spot
Browse records opens the raw rows of the last measurement: filter by type and time, search the payload, and a sequence number that holds across the whole file. Marking and hiding is crossing out in the printout — the stored measurement and the export are untouched.
Keys carried to the edge
Hold Start, Reset or Stop and drag it to the bottom edge of the display; there it stays put while you scroll anywhere. Let go outside a berth and the key swings back with an overshoot as big as the distance it travelled.
Sensors that are not in the phone
BTHome, Ruuvi, ATC and pvvx, Eddystone telemetry. Read straight from the Bluetooth scan that is already running: nothing to pair, nothing to connect, no new permission. The values land named and in SI units, beside the bytes they came from.
A panel you can
put your thumb on.
Version 1.2.0 turns the screens into the front panel of an instrument. Switches light up as a whole, keys sink into their base under the thumb, and colour is left to mean a reading — everything else is grey.
Switches that light up as one
The switch is a rocker from a switchboard, cast from translucent red plastic. Switched on, the whole rocker glows instead of a dot in the corner; the I/O marking stays readable in both positions and the rocker always leans to the side that applies.
Keys that stand on a base
Start, stop and the export keys sit on their own base and a press sinks them into it, the same as the buttons here on the site. Haptics answer in the same order: a click going down, a quieter clack coming back.
Grey panel, colour that means something
The panel is neutral grey, so every colour on it is a reading: green for controls and for running, amber for warnings, red for stopping. A screen grid with divisions and dashed axes lies under the content.
Half the download
The release build is shrunk and optimised by R8, which took the bundle from 8.3 MB down to 4.3 MB, and the outdated library Google Play kept reporting is raised through the services that pull it in.
Edges instead
of pebbles.
Version 1.1.0 stops the app looking like a sketch. Shapes go to the right angle, measured values get a dial typeface, and selections become rows that say what each option means.
Sharp edges and a dial typeface
Cards, fields and buttons keep at most two pixels of rounding, and measured values are set in a face where every digit is the same width — a column of numbers no longer dances under the eye. Spacing sits on a four-point grid.
Rows with a description, not pills
Technologies, presets and targets are rows with the current value on the right. On a source with parameters, tapping the row switches it and the chevron opens its settings — a pill could not tell those two apart.
Units say what they changed
Switching units used to close the menu and leave no trace. The dialog now says what it switched to, where it shows up, and that the export stays in metres.
Out of testing,
into the world.
Version 1.0.0 is the first public release. The instrument itself is unchanged; what is new is that anyone can install it, try it for an hour before paying, and read the screens in their own language.
An hour of measuring, on the house
Every phone gets one hour of measuring time a year, split across as many measurements as you like — the tool is meant to be tried in the field, not from a screenshot. The remaining time and the date it comes back are shown right above the Start button.
Bought once, not rented
Unlocking is a single in-app purchase at the Google Play price for your country. No subscription, no expiry, and it follows the account onto every other phone you sign in to.
Permissions explained before they are asked
The first launch no longer opens with a stack of system dialogs. A screen says what each permission is for — and that location is what Android ties cells and Wi-Fi to — and the system asks only after you press the button.
Screens in your language
The app and this site speak a whole range of languages, chosen by the phone or set for Signal Collector alone. The export never follows: it stays in SI, UTC and English column names, so two files from two countries are still one dataset.
Ready for the world
and for the Store.
Version 0.10.0 completes the move to the production identity, adds full English and US units, closes the release blockers and gives the instrument a calmer, more precise visual system — without changing how it is operated.
English and Czech, neither one a bolt-on
Text is no longer produced inside the collection layer, and errors are no longer recognised by their wording. The language can be switched for the app alone, and an English phone never gets half-Czech screens. Numbers follow the locale; the export deliberately stays stable.
Metres, feet and miles
Units can follow the phone automatically, or be forced to metric or imperial in the settings. Only the screen and the notification are converted; the database and the scientific export always stay in SI.
A release with no silent traps
The production bundle requires the upload key, targets Android 16 / API 36 and carries the final identity app.signalcollector. Corrected permission checks close the crashes that followed a revoked permission, and the updated SSH client brings security fixes.
Around the globe
runs time itself.
Inside the globe sits only what has a bearing. Quantities without direction got their own bands outside the horizon, the operator composes the instrument themselves — and measured data can finally leave the phone by a route other than the share sheet.
Four quantities in the ring
Noise, temperature, pressure and now light. The angle along a band is time, not bearing — one minute split into seconds, so the head of the trace sweeps like a second hand with a gap behind it where values have aged out of the minute.
You compose the view
The middle button switches off whatever the cursor rests on. A switched-off row stays in the list with its value, only struck through: the filter changes the picture, not the measurement.
Data can leave on their own
The gear icon gained S3, WebDAV and SFTP destinations. Passwords are encrypted with a key from the Android Keystore, an address without https is rejected, and the server key fingerprint is verified.
You can see
where the signal came from.
The pulsing background circle gave way to a globe of the sky. Satellites sit where they actually are — and anything without a direction lights the whole ring instead of inventing a bearing.
Satellites in their real place
Android reports azimuth and elevation for GNSS only, and the app has recorded them since day one — there was simply nowhere to see them. Colour separates the constellation, size and brightness carry C/N0, a filled dot counts towards the fix. Verified on a Pixel 10a: 20 satellites from four constellations, 14 in the fix.
What has no bearing lights the whole horizon
Wi‑Fi gives strength, not azimuth; Bluetooth gives none either, and cells report only their identity. Samples without direction therefore ripple the entire ring rather than a sector — a sector would claim the signal came from there. The ripples also rotate, so not even the tallest of them points anywhere.
It tilts with the phone, not just turns
Lying face up it looks into the zenith, held upright it looks at the horizon — and what was near the horizon moves behind the phone. Collapsed, the card leaves a flat compass with a needle to north: calm, no flicker.
Scrolling that
never jumps away.
While hiding, the header used to take part of the gesture for itself and the content was re-measured under the finger. Now it only observes the scroll and takes nothing from it.
Content follows the finger the whole time
The finger used to drag while the page stood still until the header had collapsed — and on reversing direction it expanded again first. The header now sits above the content and takes no part in scrolling; it simply moves away, taking the status row with it.
Nothing is re-measured mid-scroll
It hides by offsetting at draw time, not by changing its height, so the content inset stays constant. Measured on a Pixel 10a: 0.30 % janky frames and no missed vsync across ten drags over the threshold where the header switches.
It returns the moment you pull down
Direction decides, not position — you do not have to scroll back to the top to get the header. Because it also returns mid-page, it got an opaque backdrop; otherwise the title would sit on top of the card text.
A scan that does not
pretend to be a measurement.
Android throttles Wi‑Fi scans and keeps handing back the same result meanwhile. The app used to write it down again and again — and the export then claimed a measurement every five seconds.
A repeated scan is recognisable
Every attempt records the state FRESH, THROTTLED or UNCHANGED together with the age of the result; per-AP records are written only for a fresh scan. Without that, the data could not tell you where measuring actually happened — and for a coverage map, that is the whole difference.
Six times denser sampling
Measured on a Pixel 10a: with throttling on, 70 rejected attempts against 45 fresh scans; with it off, zero rejections and a fresh scan every 4.2 s at the median. At walking pace that is one sample every 6 metres instead of every 40.
Points on a floor plan, throughput per network
GPS gives no position indoors, so a place marker was added — you stop, mark a point, walk on. And a new optional source visits the Wi‑Fi networks you list one by one and measures their actual throughput, not just their signal.
Every second
gets its own row.
Continuous internet measurement no longer leaves holes in the timeline. When measuring is impossible, the reason is written down — and a Wi‑Fi network that is gone is recognised at once, not ten minutes later.
A second without a measurement is still a row
A capacity burst or a manual speed test holds the link for several seconds, and the data used to be left with a gap — a full minute in the worst case. Now it says BUSY, naming who held the link. A missing second cannot be told apart from a failed measurement; a written one can.
A dead Wi‑Fi is recognised immediately
After losing Wi‑Fi, the app stayed bound to a network that no longer existed, and over six hundred samples claimed the internet was not answering. The handle is now dropped as soon as the system stops knowing about it, and the app waits for a new Wi‑Fi with internet.
A sample knows which Wi‑Fi it came from
SSID and BSSID were added to the quality record — until now only the direct Wi‑Fi source knew them, and measured quality could not be tied to a network. Android placeholder values (RSSI −127, frequency −1) are also left empty instead of looking like readings.
From your pocket you can tell
how the run is going.
The notification for a running measurement no longer just says “collecting data”. It shows the duration and the record count, refreshes every five seconds and speaks up when data stops being stored.
Time and count in the notification
On a dark screen you see 00:02:43 · 29,880 records instead of a terse line. The duration is pure collection time, the same as on the status card — a pause between Stop and Start does not count towards it.
Data loss reports itself
As soon as samples are dropped, their count joins the line, and the title changes when writing stalls or fails. It is the one thing worth reporting before the operator looks at the screen again.
Ready for Live Updates
The notification declares itself to the system as a Live Update — Android's counterpart to the iOS Dynamic Island, a strip inside the status bar itself. On the Android 16 build under test it does not render yet, because that part of the system is not switched on; the app is waiting for it, ready.
The colour tells you
what was just captured.
A wave crosses the background every time something is written — and now in a colour that says where the sample came from. From across the desk you can see not only that data is flowing, but what is being heard right now.
A colour per source
Green is sensors, blue networks, amber GNSS and violet Bluetooth. Sensors run at 50 ms, so green is a continuous swell with the other colours flashing through it — a blue flash is a network scan, a violet one Bluetooth.
The wave keeps off the text
It used to be drawn over the content as well, tinting the title in the header, the messages and the status row. Now it sits at the very bottom: it passes under the header but leaves the type alone.
Content runs under the bars
When the header hides on scroll, the cards continue under the status bar instead of stopping at it and leaving an empty strip above. The wave shows through under the bars too.
Start no longer overwrites
work in progress.
Start resumes the last measurement instead of quietly replacing it with a new one. Beyond that, the phone lets your pocket know when the connection drops or data stops being stored.
Start continues, it does not restart
Until now every Start opened a new measurement and the previous one became unreachable — it stayed in the phone, but only the new one could be exported. Now it continues, and a clean slate comes only from Reset, which deletes the previous measurement.
A pause does not count towards the duration
The duration is the sum of the time actually spent collecting, not the span from the first Start to the last Stop — for a run interrupted overnight that would claim fifteen hours of collection. In the export it is running_ms.
Interruptions are in the data
Every stop and every resume adds its own session record with a timestamp. The data therefore shows when collection ran and when it waited, so a pause is not mistaken for a hole in coverage.
A buzz at a hole in coverage
Losing the connection is a soft thud, regaining it two light taps, a failed write three firm knocks. The phone is in your pocket while you walk, and these are the events the screen cannot tell you about. Every buzz goes into the data as haptic, so a window can be cut around the vibration.
The counter runs live
The count is no longer sampled. At two thousand records per second it used to jump by more than five hundred; now it flows, and only the digits slow enough to read are animated. The figures have fixed slots and sit on the baseline.
A panel instead of a form
Start, Reset and Stop are solid colour fields — an unavailable switch turns translucent but keeps its colour. Export got its own plate with a label on which the size of the pending file grows, and a green wave crosses the background with every written sample.
How much ground
we actually covered.
This version adds distance walked next to the duration, in a way that does not credit metres to a phone lying on a desk. Beyond that, the capacity burst shows its progress and technology selection is driven by presets.
Distance walked, in metres
The status card shows Distance instead of a static source count. The value is stored with the session, so a finished measurement still shows it after an app restart, and in the export it is distance_m.
Metres, not GPS noise
A walker covers about 1.4 m between one-second fixes, while the uncertainty of a single fix is usually larger. Distance is therefore not measured between neighbours but by moving an anchor once it passes the threshold max(3 m, accuracy).
Location accuracy on show
The accuracy of the last fix sits under the metrics. When the position is too coarse to count towards distance, the card says so outright, so a number that will not move has an explanation.
The capacity burst shows its progress
A new record for the start of a burst puts its beginning into the data, not only its result. Meanwhile the UI runs a countdown next to the transport, and a burst interrupted by Stop is not left hanging.
Technology presets
“All” and “Clear all” became a single switch, with Default in front of it. The app recognises hand-tuned sensor values, asks before overwriting them and offers to keep them as the Custom preset.
Legible messages
A dark treatment tinted by message type, dismissible by dragging down. An error stays on screen for 15 seconds, an ordinary notice disappears after four.
Internet mapping
while moving through a building.
Continuous transfer mapping got its own card ahead of Start, a heartbeat began watching collection from the inside, and a code audit cleaned up the bindings to Android callbacks.
A card of its own for mapping
A separate card keeps continuous mapping apart from the one-off speed test. It can measure Wi‑Fi, cellular data or both transports at once over a specific Android Network.
A data estimate up front
The interface shows the upper bound before you start: at most 204 MB per 30 minutes for one transport and 407 MB for both.
A heartbeat over collection
A running check of the collectors, the writer and the write queue. The session then distinguishes an ordinary Stop, a writer failure and an interruption after the process died.
The export admits its gaps
The header carries the last stored timestamp, the trailing gap and the counts of accepted, written and dropped samples.
Audited callbacks
Registrations for GPS, GNSS, NMEA and navigation messages are visible in the export itself. Bluetooth Classic stores the states of the discovery cycle as well as the devices actually found.
Fixes from the code audit
The duration of a finished measurement is computed from stored timestamps, stopping the mapping leaves no NetworkCallback hanging, and sensors deliver data on their own thread.
Maintenance that
stops dropping samples.
No new measurement feature. A version born from a code audit, fixing the reliability of collection, writing and export, and moving the format to V3.
Dropped samples on show
When writing falls behind, the count appears in the app and goes into the header as dropped_samples. Samples used to vanish unannounced; ending a measurement no longer loses the last of them either.
Ranges hold
A setting outside the allowed range is pulled back into it, so a zero interval no longer spins a scan with no pause.
A disabled Bluetooth is recognised
With the adapter off, the sources are not marked as measured and ADAPTER_DISABLED goes into the export instead of a blank.
Collection off the main thread
The GNSS, location, Wi‑Fi RTT and cellular callbacks run aside, so raw GNSS no longer slows the controls. The microphone is released only after the read completes.
Format V3
SIGNAL_COLLECTOR_TXT_V3 adds the dropped_samples header and drops the source_timestamp_ns column, which only duplicated elapsed_realtime_ns.
Schema 2 without losses
The database moves by migration and existing measurements survive. Temporary files created for sharing are cleaned up, so the cache no longer grows by a whole measurement.
Transfer quality,
measured continuously.
Alongside the one-off speed test there is now a per-second stream of samples of real download, upload and RTT — bound to a specific network and enriched with radio context.
A sample every second
The measurement runs from Start to Stop and produces roughly one network_quality_sample per second.
What a sample holds
A 64 KiB download, an 8 KiB upload and three small HTTPS RTT probes. The output carries the real transfer times, short-term throughput, RTT min/avg/max, jitter, errors and timeouts.
Capacity burst
Every 30 seconds a network_capacity_probe is produced with a 1 MiB download and a 128 KiB upload.
Forced transport
The test can be sent over a specific Wi‑Fi or cellular Android Network, even when both are available at once.
Radio and location with the sample
Every sample carries the last Wi‑Fi or cellular radio context and the last known location, including its age.
Quality, not a record
The small samples are labelled as measurements of quality over time, not of maximum internet speed. The server layer supports the CLOUDFLARE, CUSTOM and LOCAL modes.
Controls that
stay where they are.
A small interface release. Actions no longer move with the state of the measurement, the top bar gives room to the content, and a message can be dismissed when it is in the way.
Download and Share stay put
The buttons keep their place. Without a finished measurement they are dimmed and inactive, not hidden.
A vanishing top bar
It hides when you scroll down and comes back when you scroll up.
Recommend from the bar
Prepares a new e‑mail with no recipient filled in, carrying a subject, a message and links to the app.
Dismissible messages
Status notices are a bottom message that can be closed; otherwise they disappear on their own after a longer interval.
The storage note moved down
The note about local data storage now sits at the very bottom, visually subdued.
Active scan
and a measured speed test.
This version introduces an experimental active cellular scan with an exact reason for refusal, and a full speed test bound to the transport actually chosen.
Active scan events
Unambiguous ACTIVE_NETWORK_SCAN_REQUESTED, STARTED, RESULT, COMPLETE and FAILED instead of guessing support from the phone brand.
The exact reason for refusal
A failed scan stores the numeric code, the exception type, the message, the carrier privileges state and the state of the MODIFY_PHONE_STATE permission.
Kept apart from passive cells
The result carries scan_mode=ACTIVE_NETWORK_SCAN and only the operator Android supplied; an unknown one stays UNKNOWN.
A test over the chosen transport
Manually over MOBILE, WIFI or sequentially BOTH, with the traffic genuinely bound to the requested Android Network. The options offered follow the validated networks available.
A complete test summary
speed_test_result carries download and upload in Mb/s, bytes and times, the minimum, mean, median, maximum and p95 RTT, jitter, packet loss, errors and the server — together with the last cell or Wi‑Fi context.
Collection that survives
The measurement continues in the background through a foreground service, preferences survive a restart, and from an estimated 10 MB upwards the export preselects GZIP.
Installation
Installed through
Google Play only.
Get it on Google Play
- 1
Install from Google Play — no invitation, no tester list, no waiting.
- 2
Measure for up to an hour a year without paying anything.
- 3
Unlock unlimited measuring from inside the app whenever the hour stops being enough.
Google Play is the only distribution channel: it signs the update chain and no direct APK is offered anywhere. The app itself needs no account of ours and no server of ours to run.
Trial, price and support
An hour a year
to make up your mind.
A field instrument cannot be judged from screenshots, so Signal Collector hands every phone an hour of measuring time a year — enough to walk a route, watch the ring fill and open the export. The hour is counted in measuring time, not in runs, so it can be spent at several places on several days. When it runs out, unlocking is a one-off in-app purchase at the Google Play price for your country: no subscription, no renewal date, and it carries over to every phone signed in to the same account.
1 hourof measuring time free, renewed every year
One purchaseunlimited from then on, on every phone of yours
24 hoursfrom a review to a triaged issue
Feedback goes through the Google Play review; every new review is picked up within a day, turned into an issue and answered, and fixes ride the next update. The paid app carries no advertising, no analytics and no third-party SDK inside the measurement — the price is what pays for the development instead.
What the app actually collects
From physical sensors
to the networks around you.
Every source can be switched on or off individually before a measurement, and for selected technologies the interval can be set as well.
Cellular network
Serving and neighbouring cells, LTE/NR/3G/2G parameters, registration changes and the experimental active scan.
GNSS and location
1 Hz GPS, satellites, raw GNSS measurements, clock, AGC, navigation messages, NMEA and antenna info.
Wi‑Fi and RTT
The current connection, nearby APs, Wi‑Fi 7 MLO, capabilities and RTT/FTM ranges to supported access points.
Bluetooth
Classic discovery and the BLE advertising payload, including manufacturer and service data.
Sensors and noise
Motion, magnetic field, pressure, light, proximity, rotation vector and an indicative dBFS level with no audio stored.
Network and transfer
Per-second samples of real download, upload, RTT, jitter and timeouts, 30-second capacity bursts, and binding to a specific Wi‑Fi and cellular network at the same time.
SIM and eSIM
Slot, operator, MCC/MNC, roaming and which card carries the data — cells on their own name the transmitter, not who was looking at it. Neither ICCID nor EID is recorded: they are permanent subscription numbers that outlive even a change of phone.
External sensors
A sensor that is not
inside the phone.
The phone measures what it can reach. A probe on the wall, a meter on a cable, a receiver on the roof — those have to get in some other way. There are four ways in, and the first one already works.
Sensors that broadcast · working now
BTHome, Ruuvi, ATC and pvvx, Eddystone telemetry. Nothing to pair and nothing to connect: the sensor calls its reading into the room and the scan that is already running hears it. Temperature, humidity, pressure, CO₂, particulates, voltage — named, in SI units, in the same file as everything else.
Bluetooth LE profiles · planned
Environmental Sensing describes its own measurements, so a meter nobody has ever heard of can still be read together with its unit. Next to it the standard profiles — battery, thermometer, location — and the Nordic UART service, which is how a home-built probe speaks.
A serial line on a cable · planned
CDC-ACM, FTDI, CP210x, PL2303, CH340. Five families of chips cover nearly everything that plugs into USB and is not a disk: Arduino and ESP32 boards, u-blox receivers, spectrum analysers, meters that answer in SCPI.
A device on the local network · planned
Found over mDNS, read over HTTP or as a plain TCP stream. The request is bound to the Wi-Fi network, so it does not leave through mobile data and get lost on the way to a machine one room away.
Nothing is guessed. A reading the sensor itself marked as invalid is left out instead of being written as a number, an encrypted payload is recorded as encrypted rather than decoded into fiction, and a format the app does not know stays in the file as raw bytes. The keys are listed in the data dictionary.
Controls outside the app
A key that does not need
the app opened first.
Measuring in the field means one hand on the phone and the other on something else. Every control that matters therefore has a place outside the app, and each of them sends exactly the same instruction the screen sends.
Measurement panel
A widget that starts the set of sources and the intervals saved in it. While it runs it says so, carries the numbers of the measurement, and a second tap asks before it stops. The key holds its own copy of what it starts, so switching a preset in the app later does not silently change what the home screen measures.
Mark point
Up to four of your own labels side by side — doorway, corner, window are one tap each, written into the point straight away. With nothing running, the key starts the measurement and marks the point in one go.
Source tile
One source as one large number: access points in range, satellites in the fix, loudness. A tap while nothing is running starts a measurement with that source alone.
Source readout
Up to six sources, one line each, in the order you picked them — a list to be read at a glance instead of searched.
Tile in the quick settings
Start and Stop from any app and over the lock screen. It measures with whatever the app measured with last. Over a secured lock screen it asks for the phone to be unlocked first: what starts is location with a microphone.
Shortcuts under the icon
A long press on the app icon offers Start while nothing runs, and Stop with Mark point once something does. The point is marked without a label — labels are on the widget key, where there is room for them.
The notification
While measuring it carries the duration, the record count and the walked distance, with Mark point and Stop underneath. Start can be kept in the shade the whole time nothing is running, so a measurement taken in sections does not mean finding the app every time.
The keys are redrawn by the measurement itself, once every five seconds — a widget cannot be fresher than the app that feeds it. That is why each key carries the time its numbers were read at; the stopwatch is the exception, it ticks on its own. All of them are set up in one place, Home screen keys in the settings menu, and described in the help.
Field check, 10 August 2026
Data from a real
phone.
Everything below was measured on a Google Pixel 10a running Android 16. On version 0.7.2, a single measurement in three stretches collected 87,597 records: the duration grew from 2:49 through 7:21 to 8:12, the measurement number never changed, and more than twenty minutes of pauses between the stretches did not count towards the duration. The distance figures come from a nine-minute run of version 0.7.1 on the same phone — the distance filter has not changed since.
429 mof GPS noise thrown away by the distance filter
0 mwalked by a phone that never moved
9/9bursts with a start paired to a result
The first 274 fixes had an accuracy between 9 and 114 m. Summing the distances between neighbouring fixes would give 429 m, or 28 m once coarse fixes are filtered out; moving the anchor past the threshold gave zero. The test phone had no SIM, so the cellular branch of the mapping correctly reported the network as unavailable.
Versions and material
Install, changes
and source code.
The repository stays private. Signed-in collaborators find the source code, tagged releases and APK checksums in it.
Release notes1.5.2 · TXT
Earlier version1.5.1 · TXT
Earlier version1.3.0 · TXT
Earlier version1.0.0 · TXT
Earlier version0.10.0 · TXT
Earlier version0.9.2 · TXT
Earlier version0.9.1 · TXT
Earlier version0.9.0 · TXT
Earlier version0.7.3 · TXT
Earlier version0.7.0 · TXT
Earlier version0.6.1 · TXT
APK artifactsGitHub Releases ↗
Data dictionaryExport format · HTML
Source codePrivate GitHub ↗
Privacy
Measured data never leaves the phone.
The app works offline and contains no analytics, advertising, attribution or crash-reporting SDK — and none will be added. Every library the app is built from is named in the privacy policy, each pinned to an exact version, so nothing inside changes without a release that says so. The optional continuous mapping of transfer quality uses the public Cloudflare Speedtest endpoints for small test HTTPS transfers and periodic bursts; it is not a measurement of maximum internet speed. The module is off by default. If you buy the unlock, one purchase report leaves the phone and carries no measured data; it is described in the privacy policy. An export may contain sensitive location data and identifiers of nearby networks.
How it works
From a sensor
to a row in a file.
Every source runs at its own pace. A sample is stamped with a time and the last known location, passes through a non-blocking queue and is stored into the local database in batches. Underlined keys in the diagram lead to the data dictionary.
Collection settings
The same parameters the app offers for every source before a measurement starts. The ranges and the data estimate match the implementation; a change shows up in the diagram above straight away.
ms
Range 10–1000 ms
ms
Range 100–60000 ms
s
Range 5–300 s
s
Range 5–60 s
s
Range 5–300 s
Internet mappingNetwork for continuous measurement
With both selected, two separate Android Network handles run at the same time.
ms
Range 500–5000 ms
KiB
Range 1–1024 KiB
KiB
Range 1–256 KiB
s
Range 10–300 s
KiB
Range 64–10240 KiB
KiB
Range 8–2048 KiB
407 MBupper estimate of data used per 30 minutes of mapping
8 400samples per minute from seven sensors
120samples per minute from internet mapping
20Wi-Fi and cellular scans per 10 minutes
The estimate is an upper bound: on a slow link a sample takes longer, so fewer of them fit into the same time and less data is transferred. This is not a measurement of maximum speed — why.