I think I first heard about it happening someplace in central Europe some years ago, though I didn't pay much attention. What did catch my eye was the
MoboGoGlobo last March, a phone-O' put on by the Cascade OC as a fundraiser for their school program, where a local runner would be paired with a navigator wherever, just needed to have phone contact. So I teamed up with Tori Borish, lots of fun. More details of the experience
here, go down to the last entry for the day.
Rick and Susie DeWitt were also long-distance navigators that day, so it was their idea to do it at the club's winter meeting. Gail and I certainly enjoyed it and I think everyone else did.
It's normal orienteering, just the person out in the woods doesn't have a map (does have a compass). The navigator has the map, gives directions to the runner, the runner gives info in return about what he/she sees. You can move around a course pretty quickly if, and it's a big if, the communication is good. My guess is a little practice would help in that regard.
I haven't heard anything about MoboGoGlobo 2010 but I hope it happens, and I'll gladly sign up again.