Good look at the Mastercard Paypass keyfob, based on RFID technology ...
... "The new MasterCard PayPass is an RFID token that uses radio frequency keys to authorize purchases. " ...
Via Popgadget: Citibank's RFID PayPass credit card ...... "The average time consumers spend waiting in line is 7.4 minutes, but starting this fall, Citibank Banking Card cardholders in New York will begin zipping through checkout lines faster. They will be able to make their purchases quicker with the innovative, new tap-and-go Citibank MasterCard PayPass,a free, speedy companion payment device to the Citibank Banking Card, Citibank's ATM/debit card. Similarly, Citi will begin to pilot MasterCard PayPass for its credit card customers this fall. The PayPass key fob device fits on a key chain for easy access, so customers can make payments on purchases with a simple tap on a PayPass reader at participating merchants...and go. Following the initial launch in the New York market beginning this fall, Citibank plans to roll out 2.5 million PayPass debit devices across the country.

With the Citibank MasterCard PayPass, there is no need to swipe a banking card or hand it to a cashier to make a purchase. Customers simply tap their PayPass-enabled key fob on the PayPass reader at participating merchants and they are on their way. The purchase is automatically deducted from their checking account. When the lights flash on the reader, the transaction is complete. Tap-and-go convenience makes payment faster than using cash, check, even a card. Also, tracking smaller purchases is easier than when paying with cash, and no signature is required for purchases under $25 at select merchants. " ...
Via Mastercard International: Citibank Introduces Tap-and-Go Convenience for Its Debit Customers: Citibank MasterCard PayPass Fits on a Key Chain, Does Not Have to Be Swiped or Handed to a Cashier, Saves Time ...Labels: card, card-reader, credit-card, devices, keyfob-rfid, market, reader, rfid-card, rfid-checkout, rfid-device, rfid-pilot, rfid-reader, roll-out, tracking