[gotodengo]

Looks like those generic rings are supported by gadgetbridge[1] so barely any hacking needed for 100% on device processing and storage.

I have a miband I use with gadgetbridge. I'm reasonably happy with the app, and it has visibly improved over the last year (it also wins by default being opensource + the only option for keeping data private) but the watch is a bit bulky when sleeping or typing so I stopped wearing it.

I can't imagine $10 hardware will be particularly accurate, but cheap price + data control is enough to give me an excuse to play with one.

[1] specifically rings intended to be used by the QRing app - https://gadgetbridge.org/gadgets/wearables/colmi/