StealthLogger In development

Gyro data, baked into your footage.

StealthLogger logs your iPhone's gyroscope at 100 Hz while you shoot, then writes it into the video file as a CAMM track. Gyroflow reads it straight out — no sidecar log to keep paired with the clip for the rest of its life.

Rotation rate rad/s · sample trace

  • gx
  • gy
  • gz
  • 100 Hz

writing › 1754654321123456,0.0000,0.0000,0.0000,0.0000,0.0000,-1.0000

Signal path

  1. Record

    Start a session, then shoot with the Camera app. Motion is sampled in the background and written straight to disk as you go.

    stealthlog_20260808_142208.gcsv

  2. Embed

    Pick your clips. Each is matched to the session recorded around the same time, then remuxed — the video is copied, never re-encoded.

    stealth_remux_20260808_143112.mov

  3. Stabilise

    Open the result in Gyroflow. The CAMM track is picked up on import with nothing to line up by hand.

    Gyroflow · auto-detected

The readout

You spend the shoot inside a different app. The awkward question is whether logging is still alive back there.

So the session reports from the Lock Screen for as long as it runs: elapsed time, samples captured, and the rate they're actually arriving at.

That last figure is the one worth watching. It should sit near 100 Hz — if iOS throttles the sensor or deprioritises the app, it sags, and you find out during the shoot instead of after it.

An iPhone Lock Screen showing StealthLogger's Live Activity: Logging gyro, 996 samples, 0:16 elapsed, 99 Hz

Hands-free

Four actions — Start Gyro Log, Start Gyro Log (Stealth), Stop Gyro Log, and Is StealthLogger Active — are available system-wide the moment the app is installed: Siri, the Shortcuts app, Spotlight, the Action Button. No setup step.

Stealth Start and Stop run without opening the app at all — no Lock Screen indicator, no switching away from whatever you're filming with. Is StealthLogger Active returns a plain Boolean, so a shortcut can check before deciding what to do next.

The iOS Shortcuts app searching StealthLogger, listing four actions: Is StealthLogger Active, Start Gyro Log, Start Gyro Log (Stealth), and Stop Gyro Log

Screens

StealthLogger's Record tab during an active session
Session running
The Gyro Logs tab, listing .gcsv files grouped under Today and Past
Logs by day
The Encoded Media tab, listing finished .mov files with their sizes
Finished clips

Spec

Sampling
Gyroscope and accelerometer, 100 Hz
Log format
Gyroflow IMU log v1.3 · orientation YxZ · tscale 1e−6
Embedding
Native CAMM metadata track, remuxed without re-encoding
Clip matching
By creation timestamp, within a 300-second window
Batch
Many clips per session, each matched independently
Readout
Live Activity on the Lock Screen and Dynamic Island
Automation
Siri, Shortcuts, Spotlight, Action Button — start, stop, check status
Requires
A physical iPhone · iOS 16, or 16.2 for the readout