I'm so excited to play with this. I just ordered one. I've gone through two Oura rings (I do not reccomend). I'm not sure this will be reliable but it cost me $14.00 not $300 and doesn't charge me monthly to access a mediocre api.
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Im eagerly awaiting a ring sleep tracker like it which can be used offline with gadgetbridge or something.
I wasnt expecting the colmi to be accurate for this low price, but still.
For gadgetbridge I dont think there are any good sleep trackers and the only two I know of that are genuinely accurate are the apple watch and oura (theres a guy who tests them all on youtube - this is what he found).
Id happily pay extra for a decent non-apple local storage only fitness tracker which integrates with OSS and doesnt upload every heartbeat to the cloud but it does not seem to exist.