Need to use your smartphone as a credit card? There is an app for that. Sort of.
Simply sign up for the service and download the app. In a short time, a white plastic square, about the size of a quarter, will show up in your mail.
Attach the device to your phone and charge away. Simply remember that credit limits still apply.
Square will take 2.75 percent of the transaction price and tack on a 15 cent fee as well.