Professional C# .NET developer, React and TypeScript hobbyist, proud Linux user, Godot enthusiast!
https://pine64.org/devices/pinetime/
Be warned though, the hearth rate monitor doesn’t work particularly well. And there is no sleep tracking afaik.
If you’d prefer something more reliable (but less open), GadgetBridge is an Android app to interface with commercial smart watches through reverse-engineered protocols.
1099$, seriously? 😅