How much $$$ are you willing to spend? I'm an instrument engineer in R&D and could recommend some fairly pricey, high quality stuff that would be sweet. Could also recommend some instrument vendors/companies. Some of the hardware even has removeable flash media, so you wouldn't need an onboard computer.
If it was me and I had the $, I'd would run the onboard computer and make a dash mounted digital gauge screen, recording data all day long where ever I could. I sorta get a kick out of colored lines on charts though.
There are a few packages out there that racers use to record and display data, but those are pretty pricey also.
PM or reply if interested...
-JJ