It's not just the lack of API's that makes it hard for digital health startups, a big hurdle is the perceived lack of security of a cloud based solution in regards to health care data.

A friend of mine works for a digital health startup, and the majority of the RFP's they receive automatically disqualify them if they have anything hosted in the "cloud", so they are forced to buy and maintain all of their own servers.

In addition to these costs (which could already be considered prohibitively expensive) they have to use enterprise versions of proven ETL and BI tools for the perceived added security benefits (i.e. they can't use open source).