Accept credit card payments with your cell phone

From SquareUp.com:

Read payment cards from any device with an audio input jack, including your mobile phone. Accepting payments has never been faster or more convenient.

From Fast Company's article:

By providing a basic, easy-to-use and secure system (no credit card data is stored on the iPhone in use) Square could turn almost anyone into a credit-card accepting merchant. It also costs way less than the typical wireless keypad/printer card machines you see in stores, even factoring in the price of the iPhone--partly due to its "no contracts...no hidden costs" promise.