After working with a few different systems; The most usefull data is speed and throttle setting,interfaced with time and video. This gives you valid turning points in relation to actual speed and throttle position. Steering wheel value is also a speed increaser. If the driver is adding wheel as he approaches the apex, etc.
Also; I have found a lot of info, just watching the steering wheel angle values. Lots of drivers cant tell me what the car is doing, push/loose whaterver.
The video, pointed at the steering wheel and tach can be as useful as any basic system,IMHO. Add a full throttle dash light, along with a brake light for a lot of referance values, very cost effective.
The trackmate needs another car to go faster. But has alot of Data.
There is a Vortex discussion on this also,under road racing.
Mike Ogren