Square Credit Card Reader
I have the white version of this reader from Square, and it works. It's actually kind of neat how it works. You apply for a free card processing account (no monthly fees, no batch fees, just 2.75% on swiped cards, including Amex!), plug the small reader into the headset jack of your iPhone, iPod Touch, iPad, or Android device, load a free piece of software, log in, and start accepting credit card payments. The buyer signs the authorization right there on the touchscreen device, using their finger as the pen