(Perhaps such an app exists; I'm too far away from an iTunes-capable computer right now to check.)
I was in a (non-life-threatening) accident last week and I can think of a couple of useful first-aid pointers lots of people overlook, like:
* so what is the local emergency number? (based on GPS position) * "let's give him something to drink to comfort him ..." (Don't !)
Basically a decision tree to help people with basic first aid. These protocols exist in the first aid world.
I like the idea of a decision tree. Big readable decision screens: "Does the person answer when spoken to? [YES NO]" etc.
Google e-IMCI to see some actual research in this area, maybe you'll be inspired, though that is focused on more formal procedures for nurses (like detecting what's wrong with a sick child).