I tried out one of the CareKit apps this morning (I think the first four were released today) and they're really nice. Very simple, good use of notifications to remind the user to take pills/add progress, and they're still useful even if your doctor isn't signed up.
I wonder why Apple is the only big company doing something like this? It just seems like a really great idea and I'm surprised Google for example hasn't got in on it (that I know of).