Here's one of those GPS devices like the Vulocity Mileage Logger that can be used for good or evil, the $300 TrackStick Pro. Its 4GB flash memory dwarfs that of its 1GB TrackStick predecessor, and stores readings of date, time, location, speed, direction, altitude, signal strength, and temperature at intervals you select between five seconds and 60 minutes. For power, it uses either the car's accessory outlet or it can be hardwired, and its data can be downloaded into a PC or Mac via USB.
If you're looking for real-time GPS tracking data, you'll need a device such as the Worldtracker SMS, which shows your location on Google Earth, but that's a $600 unit plus the cost of a subscription. This one just records data, useful info for tax-saving travel expense reporting or perpetrator incrimination. Good or evil, it's your choice.