Show HN: Alternative FOSS companion app for new Casio F-B100W

An alternative FOSS android companion app for the new Casio F-B100W

In the contrast to the bloated adware official app, TRRRST Watch focuses on the actual watch features - simple steps, alarm, settings you need. No online account, telemtry, ads, or proprietary dependencies. The app does not even request the Android INTERNET permission, all works fully offline and private!

It's a result of reverse engineering android bluetooth logs from the original app and prior work by gshock_api, more acknowledgemts below.

Android 8.0 (API 26) or newer

Bluetooth Low Energy

Casio F-B100W in any color should work

The app requires Bluetooth/nearby devices permission but does not need internet access at all.

The F-B100W advertises only briefly, hold the left bottom 'C' button to connect. Start a connection in the app, then you can wake up the watch while using the app unless you push another button that disconnects.

Grab a signed release right here on github or wait for F-Droid to list it.

You can also just tune it to your preference and compile it yourself!

JDK 17 and the Android SDK (platform 35) are required.

./gradlew testDebugUnitTest assembleDebug

The debug APK is written to:

app/build/outputs/apk/debug/app-debug.apk

Install it on a connected device with:

adb install -r app/build/outputs/apk/debug/app-debug.apk

Or copy the produced APK.

TRRRST Watch builds on public reverse-engineering work by the Casio open-source community:

The following tools were also useful during protocol research:

This is an independent, unofficial project and is not ffiliated with CASIO. CASIO and F-B100W are trademarks of their respective owner. No Casio applicationcode, images, or audio are included.

Use at your own risk. Firmware modification and memory access are not features of this app. When poking in memory I already soft bricked the watch once, had to take it apart and restart so be careful!