Ask HN: What are your favorite Apple iOS HealthKit apps and devices?

As the years go by and I am starting to think that maybe, just maybe I will not live forever, I am starting to get more and more interested in the Apple iOS Health app and I am looking for ideas how best to use it and how to get the most of all possibilities and data that can be collected and analyzed, so what are your favorite applications (and devices) and how do you recommend to integrate them and use them...

Thanks a lot for taking the time!