Square

Alternatives: None

You probably have no need for Square, the little plastic device that plugs in your iPhone and allows you to accept credit card payments right on your phone. Developed by Twitter co-founder, Jack Dorsey, Square revolutionized small business by putting the power of checkout into the hands of people who wouldn't otherwise have it. Square exemplifies the type of apps that make the iPhone such a diverse tool. Without such apps Windows Phone 7 will not tackle the iPhone.