These have been around for awhile. Basically they're like those little cellular GPS location messengers except that they use the satellite phone network to send out text messages instead of using the cellular network. They might be useful out at places like Black Rock, but at $150 per year + another $50 per year if you want the tracking to go on for more than 24 hours it could be an expensive alternative, particularly since you have to shell out that much for every device that you purchase.