This is from earlier this year, but I didn't see how it was done - so here it is. Ever want to make your own TRON lightcycle game? But not a video game, real life! Here's a page that details how a group of racers hacked up gear and software to make a real life TRON racing game. Ingredients: "gps-receiver, backpack with laptop(Tatonka Serverpack with Gateway Solo 2500), keyboard, trackball (from old broken laptop), helmet (giro switchblade) with display (old viewfinder)" Link.
http://blog.makezine.com/archive/2005/12/the_real_life_tron_race.html