GPS based security vs. Lojack?

Does anyone have experience with GPS based security devices as opposed to Lojack?

The last time I shopped for one, the industry seemed to be in it's infancy. I'm surprised that there aren't companies that connect directly to the built-in GPS system and report out information.

As with most technology, the details seem to be in the software. The one I found was called MobileIQ, but I assume that Viper has something similar: Geofence, theft recovery, speed monitoring, real-time locate/monitor, remote unlock, etc.

There seems to be some added value here. Anyone have something with these features who can comment?