Contactless payment cards are one of the intriguing and promising areas in the RFID space these days.

While the Wal-Mart and DOD mandates tended to snap up the headlines, the payment systems using RFID are in much wider use and have a relatively long proven history. EZ-Pass, the toll road payment system in the United States, has been in operation since 1993. Exxon-Mobil's Speedpass, which can be used to pay for gasoline purchases at the pump, has been in the marketplace since 1997.

Mastercard's PayPass system, in which an RFID tag is included in a credit card, was announced a couple of years ago and is a newer entrant.

The interesting thing about these systems is the multitude of uses in the marketplace they can be put to.

The latest use is for the New York subway system. CNET's News.com reports:

Selected customers of the Metropolitan Transportation Authority will be able to pay for a train ride at the subway entrance by tapping or waving a payment card at a turnstile reader, much like London's Oyster card scheme allows for the Tube. MTA riders currently pay their fares by sliding credit card-like MetroCards.

Citigroup has teamed with MasterCard, which has installed its PayPass tag readers in some stations. The readers display a logo so people know which turnstiles accept their cards, embedded with radio frequency identification, or RFID, chips instead of a magnetic stripe.

Hat tip to Paul Allen the Lesser (which I know sounds like some medieval title but is actually the name of a blog by an entrepreneur who just doesn't want to be confused with the Microsoft Paul Allen).