Citibank has come out with what looks like an ordinary keychain attachment — the type that come with little flashlights or the like — but in actuality is an RFID MasterCard. The little plastic chunk contains an RFID chip that replaces the magnetic strip found on credit cards, allowing you to simply get close to a retailer’s reader to make your payment. No swiping needed. No signature needed.
The security issues involved have been discussed ad nauseum, like thieves sporting mobile RFID readers (which will intercept your data, allowing them to create duplicate tags, etc.), but many are saying that this is no less secure than a conventional MasterCard.