Yeh High Definition (HD) is the way to go, the picture quality is way better than most motorsport specific cameras, some of which have rubbish video quality. There are other HD cameras which are cheaper than the name brands eg Aiptek, Digilife and which usually weigh less then 200grams.
YouTube still degrade the picture quality even on HQ, Vimeo are supposed to be better. Here is an incar example using a Digilife 1080HD solid state pocket camera
Viewing the file direct its easy to see and read the gauges and speedo, going through YouTube stuffs that part up a bit.