If you have the free Flashlight app on your iPhone, you know how handy it is in a dark parking lot or when you discover, as I often do, that you stayed a little too long at the park with your dog and can no longer see the trail. The app activates your phone’s built-in camera flash, which you can use as a constant light source, a strobe, or a distress signal (there’s even an automatic Morse Code “SOS” setting). It also has a compass that uses your phone’s GPS to show you which way is north.
I’ve also noticed this about the app: If you point the light directly at someone’s eyes, it will effectively blind them–for the same reason people blink when you take their picture: That flash is intensely bright. I’ve tried this on a dark night and it makes the person holding the phone impossible to see. In an uncertain situation, that’s the arrangement I prefer: Me in the darkness, the other person brightly lit. The light of the flash also leaves afterimages on the retina pretty quickly, so the benefit lasts past the initial burst of light.
Unlike devices that promise to turn your phone into a Taser (I can’t imagine that ever malfunctioning, can you?), Flashlight wasn’t designed as a weapon. But like all useful tools, it has practical self defense applications.