updated 04:20 pm EST, Tue January 31, 2012
T-Mobile sells Square readers at about 100 stores
T-Mobile has now begun selling the Square mobile readers to business owners. In mid-December, the carrier began offering the hardware in a limited-time promo. The carrier is the first to sell the hardware directly, though it's available at less than 100 stores across the nation.
Buyers don't need to be T-Mobile subscribers to use the Square hardware to accept mobile payments. Square processes credit and debit card payments by taking a 2.75 percent cut from the transaction price. T-Mobile only officially sells Android devices that would work, although nothing should stop unlocked iPhones from using Square while on the network.
The readers have also been offered by Apple in its stores and have more recently been adopted by President Obama's campaign, as well as that of Mitt Romney, to raise funds.