Re: First do no harm
It is, of course, vital to understand any space thoroughly when venturing into it, and the medical field has an especially steep learning curve. The best course of action when designing a mobile health product is to include team members who know the space well and have a deep familiarity with it.
My firm has written two white papers about designing effective wearables (oriented towards the consumer space, but there are some ideas in there that you may find intriguing): http://endeavourpartners.net/white-papers/
Feel free to peruse at your leisure.