Cinnamon Development have released emergency distress beacon software for the Apple 3G iPhone, which sends out an accurate GPS location to rescuers when activated (as long as there is a phone signal!) It also works on non 3G Apple iPhones but will be slightly less accurate.
http://itunes.apple.com/WebObjects/MZStore.woa/wa/viewSoftware?id=288770664&mt=8
