Yes, I agree that it is, for the most part, worthless. But it is annoying that the darn thing isn't working correctly. And yes, it is under warranty. However, I hate like sin to take it to the dealer and leave it overnight for something so small and silly.
The good news is that it seems to be working correctly now. The LoJack tech came out yesterday (to my wife's school - she is a teacher) and looked it over. He called me and said that there was nothing wrong with their installation, but just to be sure, he switched the hot wire going to the unit to another wire. So far, yesterday afternoon and this morning, the gauge appears to be working correctly.
It's hard to believe that something like that would screw up a gauge. However, I had something similar happen to my '75 Corvette. Electric fans were installed in order a keep a high horse engine cool while idling. The control for the fans was hooked into the same circuit as the electronic ignition. So whenever the fans came on, the car would not run right. It sounds like the same situation on the BMW. Some of the wiring on newer cars is a bit of a mystery, but with the CAN networked controls and what-not, I can see where even a small load placed in the wrong circuit could cause trouble.
Thanks for all of your input. I'll keep you guys posted if anything more comes of this.