"A new iPhone accessory called Square allows users to swipe credit cards through a mini magstripe reader attached to the phone’s headphone jack.

The simple application and reader allows users to enter the amount of the purchase and immediately email the receipt to the customer, complete with geo-tagged information and the signature they managed to scrawl with their finger. While the application and iPhone accessory are wonderfully simple, there is worry about the possibilities for fraud and abuse." - PSFK