I made a simple Samsung galaxy watch app so that I can monitor some data live while I foil around the lake. I was previously using Alcor Telemetry from the app store, but it stopped working. It was also removed from the app store as far as I can tell. Right now, my app is only monitoring speed, Voltage, current in, and mosfet temperature. I determine speed using location data in mph. The app allows you to adjust the cell count, and it uses this to show average per cell voltage.
I should be able to share the apk with people if anyone is interested. I have not tried to compile it yet though. I will look into this if it gains traction. I know others have made apple watch apps so I figured I would put something out there for the rest of us.
For reference I only have a galaxy watch 4, but I believe with the API I used, it should run on anything else newer than that as well.