We don't use none of them new-fangled iphones or Squares, but we do insist on getting a CC number before we start on an emergency job. We did this mainly becuz we were getting called out and would get ten minutes from the job only to have the customer cancel, and we never saw a dime. It drove me nuts, becuz I wouldn't think of asking a service person to come running, and then cancel, even if the problem was solved. But it happens. We haven't done it yet, but if that happens, we will ABSOLUTELY charge for emergency response. Some folks want to pay with a CC, too.