Square and Intuit are facing off with their very own versions of mobile credit card technology. As mentioned previously, Square is a great solution for a vendor processing small monthly amounts and small per transaction amounts. Once you get more serious you run into issues: Process large amounts and square will hold onto your fund for 30 days. You can't accept Amex and many complain the swiper unit is easily lost. The problem with both of these solutions is the rates are far from competitive and when you process larger amounts the rate is what is most important. If you are serious about using a Mobile Merchant Service you will bes best off to find an honest credit card processor with great rates and service but beware of contracts, termination and set up fees.