Geocaching was invented by Dave Ulmer, early bizmo engineer and pioneer. His on-board GIS systems led him to many a frontier find.
However, in thinking of physically strenuous mathematical exercises, a genre, we need to accommodate lots of urban teens, may not simply assume easy access to rural areas with the wave of a magic wand.
Introducing bus and subway maps from around the world as topologically correct, yet highly simplified (schematic) is a standard data visualization segment. The next step, of actually riding the bus and train systems, in search of some treasure, is where this becomes a sport.
Student-friendly urban establishments such as coffee shops, subsidized to operate this program, might provide welcoming environments.
The video game aspects of the course would have this familiar indoor ambiance (already associated with scholarship), as students swiped their ID cards for points, went through the cartography and geography quizzes, touched base with on-line referees and/or judges, perhaps sitting in booths with branded swag (sponsor regalia).
Then its on to the next puzzle (some algebra required?).
This would be another meaning of "busing" (or "training"), as you would get small groups going between zip codes, creating more shared awareness of a city. This isn't a race or game of Survivor in which there's only one prize or winning team, although perks for being faster or first might pertain, depending on the game's design.
The point is to actually explore one's environment and not settle for a "virtual world" on one's desktop. The incentives need to be far more reliable and real than winning the lottery. You might not get cash, but you might get a 25 pound bag of organic brown rice, as one of your computerized options.
The reward system will focus a lot of human ingenuity, with participating schools getting much of the credit at an institutional level. If your school fields some teams, that may be your school's ticket to some interesting benefits. Your school will get noticed, its reputation boosted.
The more interesting versions of these games feature convergence points deliberately designed for group learning activities. Having coffee shops participate is a piece of the puzzle but not the whole story.
Many high schools already have some of the right stuff, so it might be a matter of organizing across schools, optimizing more.
On the other hand, here's an opportunity to do some basic rethinking and updating. A claymation studio need not be in the same building as a music recording studio, but better synergy might develop if they were. Include faculty from art and/or design schools among your advisers, would be my advice.
Designing these for-credit games is one thing, recruiting players another. The advertising needs to set realistic expectations. Some of the exercises shown will require mastery of prerequisite skills, meaning you might not get access to all that gear up front. That's what the reward system is about: equipping those ready for a specific work/study challenge (a role) with the requisite props (as in theater). The scuba diver needs scuba equipment and so on.
Doing some metal work for high school geometry credit is not as off topic as it sounds, if you imagine building a rhombic triacontahedron from scratch, or a geodesic sphere. But where might you go to acquire these skills in a safe environment? These are the kinds of questions our game designers need to be asking themselves and their communities. The answers will vary depending on town-gown dynamics, other factors.
Related reading: "Off Your Duff" Mathematics (math-teach, Math Forum, March 3, 2010)