Geocaching is a global game of hide and seek. Millions of waterproof boxes are placed/stowed/hidden in hundreds of countries around the world, and you try to find them. The box contains a log for you to sign and – usually – a small object for you to swap out with some small object of your own. The game is a direct descendant of centuries old games like letterboxing, scavenger hunting, and even orienteering; the difference is in the use of GPS device. Millions of people play each year.
You can use a GPS-enabled phone. Apisphere makes a handheld Geomate Jr. designed just for geocaching. It comes pre-loaded with cache information but lacks any kind of map (it only gives directions and distance), so a general GPS device might be a better choice.
It’s cool that kids can go out and make discoveries while playing this game, but they (and their parents) should be cautious regarding what kind of terrain or neighborhood they will run into on the way to the next cache.
Geocaching has been an absolute hit with my kids ever since we got a GPS for Christmas. We have been out almost every weekend. Find us as TruckBoys on Geocaching.com.
We got the Magellan eXplorist GC for Christmas and I would definitely recommend it. It syncs up with Geocaching.com, is rugged, works great, and costs only $160 or so. ;)
The boy scouts even have a merit badge for this now.