If youve ever felt a little paranoid while entering your iPhones passcode in public, consider yourself justified. A startling number of common electronic devices can be used to figure out your iPhones four-digit PIN from afar, according to a new study from the University of Massachusetts set to be presented in August. The really creepy thing? Potential thieves dont have to see the screen to figure out what youre typing. They just have to take a video of the way your fingers move. The studys team of researchers — led by Xinwen Fu, an associate professor in the schools computer