GPS hide n seek games

So has anyone seen these games they play now with the GPS thingies? It's like...they pick a theme, and hide stuff...in various places around the globe, and whoever wants to play can join in, go find a stash, and replace it with something within the theme...like they have a women's game, where the stashes have bath beads and that kinda girly stuff....We were talking about it at the open house, and a potter friend said she thought it'd be cool to establish an art theme one, or a clay-art theme one....have to scope it out and see how they get these things going...but I need a GPS so I can play too!!!!! I thought it sounded like lots of fun...