Authentication, synchronization, ticketing, etc. I'd think something like requiring you to unlock your NFC device in order to "swipe" in would be pretty nifty

Authentication, synchronization, ticketing, etc. I'd think something like requiring you to unlock your NFC device in order to "swipe" in would be pretty nifty 2-factor auth. I'd suggest taking a look at the wikipedia page, it has a list of potential uses.