In the Samsung Galaxy S6 there is a S Health app that measures heart rate, SpO2, stress and other values. It looks like I can purchase additional apps for this. Is this S Health exclusive to Samsung? When I search online Google Fit API shows up. I'm starting from scratch on my knowledge of this subject.
Background:
I want to make an app that accesses the API's above but I'm not sure if it's an Android API, Samsung API open to developers or a closed Samsung API. How does it all fit together?