Lost my phone at the office and spent 30 minutes turning the place over. Find My was disabled by MDM.

Out of ideas, I asked Claude how I could find it. It suggested tracking the Bluetooth signal strength, then wrote me a meter in about a minute.

I walked around watching the number climb. Found it.

Apparently you can just make the tool you need now.

Code: http://github.com/ben-z/findphone

ben-z/findphone

Source: https://github.com/ben-z/findphone

findphone

Locate a nearby Bluetooth device by signal strength, from the command line.

Built for the case where Find My is unavailable — for example when a device is enrolled in MDM that disables it — but the device is still within Bluetooth range and you just need to know which corner of the room it is in.

Install

Grab the universal binary from Releases:

tar -xzf findphone-macos-universal.tar.gz
xattr -dr com.apple.quarantine findphone
./findphone --help

It is unsigned, so macOS quarantines it on download; the xattr line clears that. Requires macOS 13 or later.

Build

swift build -c release
cp .build/release/findphone ~/bin/findphone

Requires the Swift toolchain from Xcode Command Line Tools. No dependencies. For a universal arm64 + x86_64 binary, which is what CI ships:

./scripts/build-universal.sh dist

Use

findphone            # survey mode: every nearby Apple handheld, by signal
findphone iphone     # hunt mode: track one device by name (case-insensitive)
findphone --list     # paired devices and their addresses

Add --sound in hunt mode for clicks that speed up as you close in, the way a parking sensor does — about one a second across a room, rising to a buzz once the signal reaches roughly -50 dBm, which is about where a laptop sits on top of the phone. It lets you sweep a room by ear instead of watching the screen. Clicks stop when contact goes stale, so silence means no signal rather than no device.

This is not a Geiger counter, despite sounding a little like one. A counter clicks once per detected particle and its rate is the measurement; here the rate is computed from the smoothed signal. Packets arrive on a fixed 0.3s polling timer, so their arrival rate says almost nothing about distance.

Add --redact if you are recording the screen. It masks Bluetooth addresses, and in survey mode replaces discovered device names with the device kind, since those names are not always yours. A public address is a stable hardware identifier and, unlike a BLE advertising address, does not rotate, so it is worth keeping out of a video.

Two things stay visible deliberately: the name you typed in hunt mode, and the names in --list, because picking a target means reading them. --list is not safe to film even with --redact.

Walk slowly and watch the bar. The reading is signal strength in dBm, which is negative and closer to zero when nearer:

Signal strength is a coarse proxy for distance. Metal, walls and human bodies attenuate it heavily, so a device in a filing cabinet two metres away can read the same as one fifteen metres away in open air. Trust the trend as you move, not any single number.

How it works

Three sources feed one reading, in descending order of quality:

1. GATT link — once connected to the device over BLE, readRSSI() returns a fresh measurement about three times a second. This is the good one.
2. BLE advertisements — passively observed. Apple devices rotate their advertising addresses roughly every fifteen minutes and only include the device name on occasional packets, so this source is sparse.
3. Classic link RSSI — read from system_profiler SPBluetoothDataType, keyed by the stable public address of a paired device.

Source 3 has a trap worth knowing about: macOS refreshes that value only every three to twelve seconds and serves a cached number in between. Polling it faster does not yield more information. Measured over 112 polls at 0.4s, every poll returned a value but the same value repeated for runs of 8 to 31 polls. The tool therefore counts a measurement only when the value actually changes, which is why the reported measurement count is far lower than the poll rate — and honest.

Permissions

Needs Bluetooth access for whichever terminal runs it, under System Settings > Privacy & Security > Bluetooth. It will say so if missing.

Limitations

• Cannot make a device ring. There is no path to that without Find My.
• Cannot give a bearing. One radio yields distance only, not direction.
• Only finds devices with Bluetooth powered on and in range, roughly 10-20 m indoors and much less through walls.