Add “Retail Payment Solutions” to the list of potential hot growth segments of iPhone accessories.

The first two players to make waves:

• Mophie: An iPhone attachment, whose only initial advantage seems to be its sleek integration with the iPhone. A simple phone case style enables full card swipe action for payments and money transfers.
• Square: Launched by Twitter founder Jack Dorsey – this tiny iPhone add-on enables secure credit card payments with payment confirmation. Both are perfect for smaller retailers and those possibly rejected by traditional merchant account solutions.

The goal is to change the way retailers accept payments; no contracts, no additional bulky equipment and greater portability for those with mulitple locations or even those without a locations. Great wireless solution for trade show vendors, artists and home offices.

Look for more features, and even some competitors, after this year’s Consumer Electronics Show.