Most biometric security has one inconvenience: you have to take an active step to sign in, whether it's putting your finger on a pad or staring at sensors. Wouldn't it be nice if simply being near your device was enough? It might happen. Researchers have created a computer authentication system that uses your heart's shape and size to sign in. It uses low-level Doppler radar to continuously scan your heart's dimensions, granting access so long as you're in the right place. In other words, Cindy-Lou Who couldn't hijack the Grinch's PC when he steps away for a coffee break.