The Square Payment System a tiny credit card reader that pops into the 3.5mm headphone jack of an iPhone, now works on the iPad and Android as well. The software is available at App Stores and Markets now, and works with a sugar cube-size device that the company is giving away for free to those who sign up.
Using it will not be free. Retailers pay fees starting at 2.75 percent plus a 15 cent surcharge, but that’s cheaper than many other options out there (Terms of Service).
Their video pitch explains the concept.