Honestly, Samsung's version of Android is modified enough to almost qualify as its own OS. But I digress.
Again, I already track all of this using built in apps. I am looking for an external device with the sensors to continuously measure things
like my Smartwatch, but for when I'm not wearing a smartwatch.
The "gold plated" version is the Oura Ring
https://ouraring.com/
But the cost is insane. By the time you buy the charger (not included), it is $350-$450 depending on the finish.