SCVNGR is a game all about going places, doing challenges and earning points. The game is played from a custom app on iPhone and Android as well as via SMS. It is not a text message scavenger hunt. Instead of riddles to guide you to a place, SCVNGR concentrates on completing challenges at a particular location.
D. Stanton, C. O’Malley, K. Ng, M. Fraser, and S. Benford. Designing for change in networked learning environments: proceedings of the International Conference on Computer Support for Collaborative Learning 2003, page 293 – 302. (2003)