Greetings everyone,
I don't remember how I stumbled onto this site. I'm not really a car guy so I'm not sure how I wound up here. But I'm also building what will be an Open Source hardware package to monitor vehicle data. I call it EM Dash but it's aimed at electric motorcycles and not cars so I'm not sure what I'd have to offer you guys other than this link I just found. I hope this hasn't been posted before.
From the website:
Xarias - Embeded AVR system for your car, based on ATMega MCU. Calculates statistics and control your car.
* calculating speed, fuel consumption, economy driving, e.t.c.
* displaying information about temperatures and controll Air Conditioning system in your car.
* controlling other devices, like electrically opened windows.
http://code.google.com/p/xarias/
There ya go. I hope that was helpful to someone.
Mike