I've never built an mhealth startup, but I have spent a lot of time researching and implementing gamified product experiences. I would suggest the following resources:

1) Anything Gabe writes + videos online
http://www.gamification.co/gabe-zichermann/

2) Anything Nir writes + watch his videos online
http://www.nirandfar.com/
On Clarity: https://clarity.fm/nireyal

3) Anything Amy Jo Kim writes + talks
http://amyjokim.com/
On Clarity: https://clarity.fm/amyjokim

These are the 3 people I turn to .. they're brilliant