We have GPS trackers installed on the install vans at my work. I've seen the real time tracking maps. They track everything about the vehicle. The speed it's driving, every time it stops, every time the engine is turned off or on, you can predict arrival time at destinations based on average speed and traffic conditions taken from online.

These are just some cheap consumer model ones the boss picked up for about $100 each.

The more advanced and expensive ones he showed me, could give you even more detailed real time.information.