My company put gps units in our trucks back in August, they haven't fired anybody based on them yet, but that is coming.
The management claims that they are only concerned about accountability of the vehicles, in the last year or so we have had company owned vehicles go missing along with the assigned driver, or end up in places they shouldn't be during non work hours (one ended up upside down in a ditch at 0300).
I know that they are comparing GPS data to fuel usage, claiming to look for ways to improve fuel usage. They have very recently turned on a software feature that puts us on and off jobs based on GPS. That kind of sucks because we have guaranteed time frames, that we are required to make, guess what happens when the customer lives 500ft off the road, the GPS doesn't know where you are, but it knows you aren't at the address you are supposed to be, so even if you manually put yourself onsite, it takes you off site and sends a message that you are fucking off instead of working.