There was a fascinating interview on the Today show of Don Woolley, an American filmmaker in Haiti who used his iPhone to help him survive the massive earthquake.

….Woolley had taken refuge in an elevator shaft, where he used an iPhone first-aid app to treat a compound fracture of his leg and a cut on his head. He had already used his digital SLR camera’s focusing light to illuminate his surroundings, and taken pictures of the wreckage to help find a safe place to wait to be rescued — or to die.

….Thanks to the iPhone first-aid app he’d downloaded, he knew how to fashion a bandage and tourniquet for his leg and to stop the bleeding from his head wound. The app also warned him not to fall asleep if he felt he was going into shock, so he set his cell phone’s alarm clock to go off every 20 minutes.

There hasn’t been any news of the actual medical application he used, and it’ll be interesting to find out in the future.  My immediate guess would be Merck Manual – Home Edition, they have a great explanation on how to treat compound fractures, but there are other first aid applications out there as well.