If you are going the USB to computer route it sounds like you are on the right track. Its kind of fun to watch the 'live' data on the screen (just not while actually driving), that is where a logging feature is good to have. The nice part about a tool like this is it will work with any of the newer cars, back to 1996 I think. Its amazing how much diagnostics one can do without opening the hood. Even if you don't end up wanting to fix it yourself you know what the service guy should be telling you
I just bought an Acer Aspire One D250-1515, in white

as an 'update' to an old PalmPilot IIIc. The back seat pocket is a great idea for storage (handy, but out of the way while driving).