The rules of business are changing. This new service can add to your success. With Square, anyone can accept credit or debit card payments by downloading the app and plugging a little plastic cube into the headphone jack of an iPhone, iPod Touch, iPad, or Android phone. After a quick swipe of the card through the reader, the merchant turns the device over to the customer to sign his or her name on the touchscreen using a finger instead of a pen. The customer can add a tip, either by percentage or a particular amount, and then enters their phone number or email address. In the best case, the receipt message will buzz in the customer's pocket as an email or SMS text message while walking away with their purchase.