Nextel has some affordable (I didn't say cheap!) programs. We also looked into it last winter to monitor our crews, but just never got around to doing it. If your crews are issued a nextel or they are installed in the truck, you can monitor them that way.
Depending on the package, you can monitor where they are, how long they've been there, their average speed, etc.
I've been using AGPS from Nextel and TeleNav for almost 2 years now. I still love it. It's FAR cheaper than even the most affordable GPS device is.
It works anywhere in the country - automatically. That is, you don't have to buy a new CD or download a new map. It just automatically works anywhere. I've used it in several states over the last 2 years, without problems.
As for price, I think it's very affordable. I think I pay less than $25 per month in total (to Nextel and to TeleNav). I've never gone over the data usage on the Nextel end.
The only disadvantage to AGPS vs. a "real" GPS system, like Tom-Tom or Garmin is that AGPS works off of triangulation of cell towers. That is, they use 3 cell phone towers, approx. 5 miles apart from one another to triangulate your position. It's very very accurate (within a few feet, actually.) But the problem is that if you are up in the hills or something, there aren't always 3 towers within the radius that this thing needs to be able to work. So every once in a while you just get a "out of GPS range" error. But honestly, that doesn't happen very often. I'd say my AGPS phone works about 99% of the time that I want it to work. And I am not willing to invest almost a thousand dollars just to get that other 1%.
Turn-by-turn voice instructions, on-screen instructions, distance remaining to destination, estimated time of arrival, etc. It's killer. I love it. I honestly can't figure out why everyone with a Nextel phone doesn't get TeleNav. I think maybe people just don't understand how simple it is. Or marybe they don't market it very well. I dunno.
there are actaully a whole range of products for tracking your vehicles using gps. Starting points are about $400 per truck and are a very useful management tool when running out multiple crews. For real time tracking, the price goes up along with the monthly fees, but there are multiple devices that just silently log the information then can be dowloaded by cable when the truck returns or via 2.4 ghz antenna when the vehicle gets in range of the base. The more bells and whistles you want, the bigger the price gets,( like in cab navigation or real time tracking). I won't reccomend one system over another because it depends on what info you want and when, but I will say that the payback time is very short. Also to be considered, if you'd just like to test whether or not gps monitoring would work for you, is to get a generic black box with an antenna and a few wires coming out of it, dummy it up to power and tell your guys that it's a gps tracker and see what happens to the time in your routes. That's a $20 test that will tell you a great deal about what your crews have going through their minds.
I use a Garmin unit on my dashboard for directions to estimates/reroutes for traffic. I wouldn't be without it now. I downloaded the entire northeast (99% of my travels) when I got it and use it almost every day.