hmmm
Well I use a real motec telemetry when I race in GTR.
http://ga-oyaji.hp.infoseek.co.jp/PC...o_MoTec_03.gif
From the hardware end of things the cars just have a number of censors on them which constantly measure things. Engine RPM, various tempretures, damper travel, wheel speed, oil pressure, pedal position, steering lock.......
All the software does it take that data and displays it to you.