Three student entrepreneurs at the University of Michigan think they can use their phones to make the world a better place, one download at a time. Three weeks since its launch at Apple's Worldwide Developers Conference, the application, DoGood, has recruited more than 15,000 individuals to be part of a growing network of users who want to change the world, at least a little. Subscribers to the free application are prompted daily with a "DoGood" -- a simple task from conserving water, to turning out a light, to beautifying the world. When they've accomplished their good deed for the day, they click the application's "done" button. The program tallies how many users are fulfilling that day's deed, and users can share what they have done on Facebook and Twitter. So far, it's up to 209,214 good deeds.