Hello, the project is based on javascript, not arduino,
The p8 watch is basically an pinetime (https://www.pine64.org/pinetime/), same manufacturer, different casing.
One can install arduino, python (wasp-os), infinitime, and many other projects on it.
I went the espruino way (javascript), I like that it is simple to program, it has an online ide (https://www.espruino.com/ide/), can write code inside the watch, and an easy to use app management system (https://enaon.github.io/eucWatch/p8).
Everything is done from a chrome browser using web bluetooth, no physical connection to the watch is needed.
Sherman and begode are just displaying speed for now, ninebot e + and kingsong have a complete client, and inmotion v11 full client is on the way.
Instructions on how to hack a p8 watch and install the project are here,
https://enaon.github.io/eucWatch/tools/hackme/