Google Fit API offers API for web as well as mobile both applications. It's fitness data is 90% accurate and userbase is strong so it could be found best in the market. Review collected by and hosted on G2.com.
This SDK documentation is not so great. This is one of the pain point. But we can found more solutions on internet in other articles. This is how I implemented the same for my product. Review collected by and hosted on G2.com.
