Amazing. Zykeband looks promising. I really like the idea of locally processing your health data, which makes lots of sense, considering its sensitive nature. A major plus, imho.

I did research Oura's ToS, they make big promises about privacy, but you have to trust them. Also, to get more out of it, you have to share quite a lot of PIIs, a huge risk, but nevertheless, I decided to go for it. I still don't regret my decision, because their app is superb, and I can see how it can/will get even better in the next years.