I currently use Fleetmatics in five trucks. Im going to get rid of it once the contract expires but not because i am not satisfied with fleetmatics. Long story, getting rid of employees for install crews and switching to sub contractors and dont need to monitor the few actual employees i have left. Fleetmatics has alot of potential if you want to invest the time in it. In addition to spying on your plebs you can use it to keep track of when your trucks need oil changes, inspected, registration renewed etc. You can also get alerts when they go over a certain MPH and it keeps track of time spent idling and a ton of other features that i never used.
Not sure what industry you're in but it has also helped me with an occasional billing dispute. Customer call up bitching because they agreed to a $400 dollar contract and say we were only there for 15 minutes. "Well Mr.Dickless, Fleetmatics says our technician left the shop at 12:17. We arrived at your piece of shit trailer at 12:43 and left your home at 2:17. Now kindly go fuck yourself."