Whereas I throw my Apple Watch in the general vicinity of the magnetic charger, it locks into place, and charges just fine, 100% of the time. Fine, don't use induction like Apple, use two exposed, flush pins and a magnet like my Coros armband HR monitor, because that works 100% of the time, too.
Apple certainly doesn't let you.
My goal is to have a cron that runs on my homelab that pulls my health data into a DB I own, from various sources, and visualize it in Grafana.
There are several apps[0] off the top of my head that pull data from Apple's HealthKit. Apple even has a framework for it: HealthKit. That said, I've never written to that API myself, but it observational evidence indicates that you can pull data from Apple just fine. The app I use to pull data off Apple and ship to Strava says as much.
[0] RunGap and HealthFit