very interesting ida but unfortunatly unless your runing linux of some real stable os in there i wouldnt even venture to have my car computer control anything OEM related maybe a window or door lock but certainly not fuel or acceleration. just imagine a blue screen of death with the computer giving the last command of limit horsepower while your about to floor it to make it across an intersection in time. ouch. eventually maybe possible as far as implementation id guess you could just limit the amount of gas availible to each user.
your better bet install a webcam and log all the trips including a video overlay of the actual speed (kind of a little black box)
then yellat you son when u see hes going faster than hes supposed to.