MobileLime solution using RFID
MobileVillage: PDAs, Handhelds, Mobile Computing & Wireless Technology for Business: "MobileLime's new quick-scan features only work with an RFID compatible phone -- currently only the Nokia 3220, though more such phones are expected in the future. The user just clicks the lime from the phone's menu screen, choose the credit card they want to use and wave their phone over the contactless reader that's integrated with the point of sale system at checkout. For added security, the user can configure a PIN required to complete each transaction."