I started this because I wanted to push structured swim workouts from my training platform to my goggles without paying for another subscription. Ended up spending an afternoon decompiling the APK, running mitmproxy, and mapping the full BLE GATT profile. The protocol uses custom protobuf schemas over BLE with MITM-protected pairing — the goggles display a 6-digit passkey on the HUD during bonding. Sync is a chunked file transfer with CRC validation. Full protocol documentation is in PROTOCOL.md in the repo. Happy to answer questions about the RE process.