Apple retailers frequently discount iPhones, Macs and iPads for Black Friday.
Square Mobile Payments Now Available for iPhone
Square is a free app that interfaces with the Square credit card reader which plugs into the headphone jack of your mobile device. Square will send the reader free to anyone that signs up. Square then charges a percentage of the sale plus 15 cents. There are no monthly minimums or setup costs. More information is available at SquareUp.