Not the parent, but I've been using the Oura ring (https://ouraring.com/) for almost a year and it works very well for sleep tracking. It's a sleep tracker above all, and has rather limited exercise tracking. It tracks resting heart rate, sleep phases, body temperature, and breathing. There's also an API to download data from their cloud service, although I haven't tried it.

I haven't yet received the newer model, but it seems to solve the issue of limited battery life in the previous model and the ring is also significantly smaller.