Tether? Check. Sticker with my number? Check. An IF_FOUND.txt in the SD card? Check. A device that beeps whenever the camera is out of range or the battery died? Huh?
I had this idea for my upcoming ski trip to get notified in case I lose my GoPro. Problem is turning on WiFi will drain the battery very quickly so I resorted to using Bluetooth, the camera spawns a Bluetooth connection when pairing, and that's not ideal for me since I need to get a BLE signal as soon as the camera boots up. I ended up finding an undocumented feature which allows the camera to pair to a BLE server of my choice whenever it boots up and has wireless connection turned on. The BLE server would be a battery powered ESP32 with a buzzer. Whenever the camera connects to the ESP32, it will turn off the LED; when it disconnects, it will turn on the blue LED and start the buzzer alerting me that I either misplaced my camera or it's out of battery, time to change the battery, and continue skiing. I plan to mount my camera on my helmet and on my ski boot, places where I cannot check if the camera has battery or not.
To access the aforementioned undocumented mode you need to use the GoPro app and have the ESP32 in server mode ready:
When the camera is disconnected, blue light on. when connected, blue light off.