Beats Pro Heart Rate Monitor - dangerous

2 Questions:

I have the latest Apple Beats Pro, and am using it in the Gym whilst weight training, etc. with my iPhone XR.

Recently it seems to stop updating periodically, and during strenuous lifting session shows my HR at its resting state for a minute of two before updating... Has anyone else noticed this ?

Secondly, I would like to create my own simple App which just displays heart rate - using this product as the data source, however there doesn't appear to be API documentation in order to work from. Am I missing anything here, or is it matter of having to reverse engineer from the bluetooth data traffic, and if I do that to create my own personal app - will I be sued by Apple for having done so ?

( I just want create a simple app for monitoring my exercise related HR - nothing more, just need reliability, which was something I thought the device offered at time of purchase).