if you are mesuring volts you are probably a ricer or didn't build your stereo right, if you need to mesure oil pressure or temps in anyway better than stock gauges then you are running higher rpms than typicaly run on the motor so i am still right.
if driven normaly the gauges given will more than suffice.
that said my car comunicates voltage, speed, RPM, lateral G force, slope angle, direction, latitude and longitude, mileage, altitude, clock, audio level meter, horsepower, and torque back to me in real time and all of these things can be recorded for study later on to improve upon my driving and my car. all this with out attracting unwanted attention from the cops and making my interior look like trash.
however i have never blamed a cop for thinking i am a bad driver as far as laws go. the attention i get is my own fault and i am more than aware of that.