Backseat Playground is a research project that developed a GPS-based game for kids. It seems more like a (great) storytelling system more than a game. Basically, it uses the GPS and location-awareness to introduce game elements, e.g., when it sees that you're driving over a bridge, it presents you with the opportunity to "explore" the river with that SCUBA tank you picked up in the last town you drove through.
What a great idea. Any story is made infinitely more appealing by tailoring it to the invididual. To present a long car-ride to Grandma's house as a detective story is a brilliant innovation. I wonder, though, if the better approach would be to feed the parent plot points as they drove, as that would be infinitely more enthralling for a kid.