Good question. In my limited research, it seems the factory system is door sensors and engine imobliization. The upgrade looks to be the addition of glass breakage sensors.
I tried to get more information...Can you upgrade yourself later? Do you get anything else besides a microphone (to listen for breaking glass) with your upgrade? And so on...
But all I received from a number of folks was shrugged shoulders. But, there are a lot of real experts here, so they may be able to provide some real answers...
It does seem like a pricey upgrade, so it'd be nice to know what it was all about..