Depending on where you're going, a non-cellular based SOS solution is a wise option as well. Something like a SPOT, or the new iPhones have satellite emergency and location options. I've had a few opportunities to test the satellite features on my iPhone (for location updates, not emergencies, but it uses the same system) and it works amazingly well. I upgraded to this new phone last summer specifically to have the satellite options for our trip to James Bay, but that never happened...but it's still there for this year, fingers crossed.