Its been awhile since I posted, but I thought I would share something I find interesting that applys to this group of people.
Check out Phidgets (www.phidgets.com). Basically, this company makes USB interfaces to other external electrical devices.
For example... if you wanted a light sensor, or a temp sensor to feed input to your car computer... PERFECT match. I'm going to use a potentiameter to read steering wheel angle.
You can also read on/off status with the "digital inputs" on the boards.. like if the door is open, or the brakes on, etc, etc.
You can also control electrical circuits with their relay board (0/0/4).
Lastly, they make some other components, like a Thermocouple unit (can read Exhaust Gas Temps) an Accelerometer (G Force), and an "Encoder" which is kind of like modern volume knobs (keeps spinning and spinning, but the knob knows how far its gone).
I don't have any financial interest in the company other than the fact that I want them to make more of these types of things (specifically I want a frequency counter to read ABS sensors). I'm working on a car computer for my H1 Hummer (http://strandtc.littleblueroom.com) and Phidgets have become the focus of my project... not playing MP3's or DVD's... (although I will probably include that functionality)
I'm working on some Linux drivers.. there is Windows support through VB, VBScript and a C library.
Anyway.. if this interests you, I would suggest checking it out. Its almost plug and play.