A buddy of mine works for a large local pest company that has over 100 trucks. They have a GPS system that the big wigs in the office have a 47" flat screen TV that they can watch each truck as it drives on our local roads. When each truck stops at the customers house they hit a "start" button and a timer starts for their time they are given to spend at that house. When the job is complete they hit "finish" and add any notes. As soon as they hit finish it automatically starts their GPS directions for the next clients house and the game starts all over.
Any truck that has gone idle for to long or off the grid will alert their manager via text.
I don't know the name of the service but I know they have spent over 100K to integrate this service and IPADS.