thank you! i think it's ridiculous how little they invest in their developer ecosystem. i have been thinking about jumping ship to oura or whoop simply because of this.

I track sleep and energy levels with a galaxy watch and there's a strong correlation with how I feel on a given day. Sometimes it surprises me, and day where I wake up thinking I slept well but after an hour or two I'll realize my energy level isn't great, and sure enough I'll check the app and see it's low, with a warning about my sleeping HRV or resting heart rate being away from my norm.

It's not perfect - there are definitely days when it's wrong. But overall I have a target of keeping my sleep and energy scores in the 90s and it's helpful. I think the most important thing is to keep in mind that it's an imperfect measurements but it's still the best one most of us have for now.

by tracking sleep, what exactly do you mean by that? sleep phases, sleep score, sleep duration?

it's a lot of work, but something you could do is track how you feel (manually or some other way) and do a similar statistical analysis. chess elo was just convenient and aligned for me.