The cards are a NFC system designed by Visa.

There is no if, its in public field trials ATM, at least one event had 200,000 people at it. Visa has deployed terminals at all the sporting events and to pubs around the stadiums.

What is going to be fun is near field sniffers, harvest peoples data etc... I can imagine walking through a crowd and sniffing out dozens of cards etc... the problem of course will be using the data, unless you can work out a way quickly convert small value purchases to cash...