To Tony's list add the Middle East. I will try southern Africa next year. I am using the Garmin Explorer, it is a great communication device, and a fair GPS mapper.
I have used the same satellite system with transmissions from lease custody units on oil and gas wells in remote areas. Even in woods and deep "hollers" you should get at least a couple of direct passes overhead each day and the message will make it.
Not perfect, but pretty good. You can also consider the various flavors of emergency beacons, but they are only for emergency.