Oyster cards are used for public transportation in London. Just swipe your card at the turnstile and step on the train.
Did you lose your Oyster card? Lucie Davis, a design student at the University of the Arts London, won't. She took the RFID chip from an Oyster card and embedded it into one of her fake fingernails. Now to board the Underground, she just taps her fingernails on the scanner.
Here's a video showing Davis's nails in action.
-via Lawrence E. Forbes