CNN: Twitter creator Jack Dorsey Wednesday gave the first public demonstration of his hotly-anticipated latest venture -- a device to allow credit card payments by cell phone -- and revealed it would be given away for free.
Details of "Square" -- a card reader which plugs into the headphone socket of most mobile devices -- have been circulating on the Internet since it was announced earlier this month, but little has been known about how it works or who it was aimed at.
