Not directly rotary aviation related, but this group is a great resources
for this kind of question...

I've got a check engine light that has been coming on and off and it is time
to buy an automotive scanner.

I'm deciding between a very basic Actron CP9410 (
http://www.amazon.com/Actron-CP9410-PocketScan-Diagnostic-Vehicles/dp/B000YIW5VA/ref=sr_1_3?ie=UTF8&s=automotive&qid=1251516358&sr=1-3)
and something more substatntial including the possibility of some kind
of
OBD2/USB based software system for my laptop.

Any specific recommendations? Someday I might be wanting to use this to tune
my turbo-compound renesis powered 4 seat homebuilt...