That blotch on the man's arm there isn't a bruise from where he was restrained by the police last night, it's a digital tattoo. A thin electronic film that sticks on and lets you securely unlock your phone with a tap of your arm, neck or wherever you stick it, using NFC.
The tattoos have gone on sale in the US, with Moto X users able to buy a pack of 10 of these digital tattoos for $9.99. They're supposed to last for five days each, until your hectic gym/sports routine wears them away. If you mostly stay at home on the internet, they might survive a little longer. [ Vivalnk via YouTube]