Earlier today I ran across this product in a pc magazine. I thought members may be interested.
It's a simple device that plugs into your car's OBDII connector and continously logs information such as trip details, including time and date, distance, speed, idle time, hard accelerations and decelerations, and engine diagnostic trouble codes.
Once the information is logged, you analyze it offline on your computer by plugging the logger into the PC via USB and installing the supplied software.
I have no idea how well this device works and I'm not affiliated with it in any way. Maybe there's somebody out there that's tried it. The price for the least costly model is $139.
Here's the link: