This pop-up chocolate store let you pay with the promise of a good deed toward a person you care for. The chocolate boxes had a range of different ‘price’ options so that people could pick a box according to the good deed they were willing to do. 
Instead of a cash register the store uses iPads where people can log in to Facebook and post their promises to the profiles of both the giver and receiver of the generous deed.

Via Jb Burdin