I recently started using Field Technologies http://www.fieldtechnologies.com, a provider of GPS fleet tracking, to track two of my vehicles. They followed through with the entire process, including installing the GPS tracking devices.
The GPS devices update every 2 minutes and report data via the cellular network. I then login to the web interface to view the path, speed, heading, address, and a plethora of other metrics and information.
Their web interface is really well done, use to easy, and makes use of AJAX. I highly recommended Field Technologies.
