Are you referring to POS terminal? By the way, you may look for a card processing solutions provider for accepting credit card payments. They will help and guide you so that the processing can be safe and secure.
I went to this coffee shop by the train station yesterday and the cashier swiped my card on something attached to her iphone or rather, the shop's iphone. It was cool. I know what you are referring to for merchant solutions, we found out about that when we were helping my cousin plan the business. Thanks for reminding me - I totally did not think of that.