A cellphone app called CauseWorld has figured out a way for advertisers to turn their marketing dollars into charitable donations, and Procter & Gamble, Citi and Kraft are on board.

When iPhone or Android users open the app, it uses the phone’s GPS to present a list of nearby stores. When they enter a store and check in — as you would with Foursquare or Gowalla — they earn so-called karma points. They can donate the karma points to their choice of 15 charities, and the advertisers make the donation.

The companies get appearances on a cellphone user’s screen and users can also send branded messages to Facebook, like “I’ve planted a tree with American Forests! Made possible by Kraft” or “I’ve provided disaster relief for Haiti with the American Red Cross! Made possible by Citibank.”