GPS will save a driver in many ways like if a parent calls in accusing a driver of missing the stop, well one can tell that parent what time the bus was at the stop and how long it was there. Good drivers don't have anything to worry about with GPS, keep the speed under control and don't idle excessivily you should be golden.
I look at it the same way, if you are doing your job properly, then there is no need for concern. Same goes with video camera systems. I don't have Zonar, but my buses are all equipped with GPS on the camera systems, some have dashcams as well. It's saved the drivers' rear ends numerous times. False accusation can be disproven quickly and efficiently.