Well this might be somewhat unusual than most of the question in here ....

I always like electronics , few days ago I found out about BASIC stamp microcontrolers .
(you can see details about these microcontrolers at http://electronics.howstuffwor...c.com )

The chips can be programmed (and reprogrammed) from a computer , using BASIC or JAVA (those are the two options offered by parallax inc)

what this has to do with cars ?
well sometimes , don't you wonder , the current acceleration or speed of the car infront or behind you ?

using this microcontrollers (and a small program with simple math) , a speedgun , some info from the ECU (or ODB ... hey i don't know much about car computers) ,
and a small LCD screen , this can be achived

what I wanted to ask , is there a website where I can get info about , how a dyno device is able to read info from the car (such as the current speed) ?

Note: I'm just messing around , Im not some great programmer/geek (btw I do program in java) , but if in theory there's no problem , i would like to try this project and get it to work.

comments on the project, advices , and the info I asked for above
are all welcome

EDIT : the reason the info from my car is needed is =>
Since both cars (me and the other car) are moving the speedgun will result with the speed difference .
Now with two reads , it will result with the acceleration (retardation) of the Other_car and me , coming together of getting away from each other .
This might be , because My_Car is slowing down or accelerating , or because the Other_car is slowing down or accelerating. If i was able to read my speed at any time , I could remove My_Car acceleration retardation , and read only the Other_car's acceleration retardation .