When you're off the grid, how can you stay in touch with civilization?
kayaked* rafted Colorado's Yampa River, where cell phone service is erratic. To reassure my wife, I brought the Spot Satellite GPS Messenger (findmespot.com, $150, plus $99 annual subscription). It's a tiny waterproof device that can broadcast pre-set messages from anywhere. Every day, I could use it to e-mail my wife that I was okay and enable her to see my location on a Google Map. The device has a button for calling in emergency workers, too, which thankfully I never had to use."
*Correction: Rafting, not kayaking. I regret the error. (Nov. 2, 2009.)