I would be interested to hear how you get on. I have a pixel on graphene and was looking to do similar. The guys on Self hosted podcast got it working with a Garmin
Discussion
Here is the link to the podcast https://fountain.fm/episode/HTq37AWHSwXfxPmAQI3P
It's going well. A few phone permission setting adjustments. Google Play Nearby devices was the major unintuitive one. Big wins are having Spotify playlists downloaded to the device and being able to play via Bluetooth headphones on the go without the phone. Exercise tracking works well. Still can't get GPay or Samsung Pay working for virtual cards, like as on Graphene in general but otherwise great.
