OK, this stuff is cool enough to make me want to keep my iPhone:
iPhone blood pressure monitors & trackers:
I'd like to design a mobile app for tracking and managing pain. Flareups and neurotoxic food sensitivities wouldn't stand a chance. Touchscreens rock for radio buttons and simple data entry; just have to make it easy to pick what you need and dump it into a dashboard with different ways of viewing the data -- historically, by symptom, by factor; graph, chart, etc.
Collecting and tracking your own data is key to surviving and thriving with a long-term condition. It is possible to make good use of gadgetry, though it's not something I usually focus on.
Any of you developers want to write the backend?