There are many such devices that could be used.. For example, I know of a couple that are targeted to parents of teenage drivers. It not only provides real-time location information, but also will record routes/speeds/etc.. for later playback. There are also several systems out there designed for tracking truck fleets real-time via GPS. Do a google search for 'GPS tracking' and you will come up with a wealth of information.
Cheers,
Brad
