What's the easiest way to find out someone's password? Watch them enter it, of course, using the simple hacking technique known as shoulder surfing. Cameras and software have successfully been used by researchers to automate and improve the accuracy of snooping on smartphone users with such observational methods, but they require a direct line-of-sight to work. Now, as Wired reports, a group at the University of Massachusetts Lowell has developed a way to capture iPad passcodes without needing any kind of on-screen cue. A camera is still required, but because the position of the lockscreen keypad is static, their software references finger movement against tablet orientation to estimate the PIN by the way it's entered.