CSO,
It's more of a safety device. It works off of satellites and only has a couple of buttons.
A 911 button, which is to be used for life threatening situations. Once the button is held for 3 seconds the appropriate agency is notified and your GPS coordinates are given to them.
A help button, to ask your friends and family to come and help you.
A check in button, to let your family and friends know you are okay.
If you pay the extra money and upgrade the service your friends and family can track your progress on a computer using Google Maps.
They have them at Cabelas, but I haven't made it over there to check them out in person yet. It could be a handy tool if you're in the back country with a buddy or by yourself. My family and friends always get nervous when I go out by myself, so I figure it will probably be worth the money if it works as good as advertised.