Hi we purchased one recently and I am testing it now on our USA trip.
seems to work very well.
I opted for the 12 month plan at $75/month which will give us unlimited sms messages to and from the device. Definately the cheapest option for basic comms in remote areas.
The tracking options will allow family and friends to see where we are and keep in touch.
I used one last year on a trip to Abrolhos Islands and it worked well.
Agree with Ross about keeping VHF HH with you at all times.