My super-cheap fitness tracker has a hidden feature that can go head-to-head with Garmin and Apple

My Amazfit Helio Strap is a treasure trove of features. I can't believe this $99 fitness tracker beats the Apple Watch 11.
Ars Technica

Cheap bluetooth accelerometer with open programming API?

I'm looking for something like this that I can write an Android app to read/log/analyze the accelerometer data. Anyone have experience with something like that? The end goal would be to wrap it in a ...