From the website:

Obopay is the first truly comprehensive mobile payment service in the United States. That means we're the only service that lets you instantly get, send and spend money anywhere, anytime with anyone. Plus, it comes with the added convenience of an Obopay Prepaid MasterCard®. Think about that for a minute. There are over 200 million cell phone users in the U.S. and more than 24 million MasterCard® acceptance locations worldwide including merchants and ATMs. Now, that's a lot of people and places that are going to love Obopay. With Obopay you can instantly pay back a friend, split a dinner bill, get money from your parents, get quick cash, pay up or collect on a friendly wager, track purchases, check your balance, and much, much more. And, you can do it all from your phone; anywhere, anytime with anyone.