In doing more digging this Actron unit, on my previous post, might be the one. You can upload your codes to a site, and have them analyzed. This gives you the power of the more expensive systems, on a temporary basis. Perfect if you only do it once or twice per year. It cost $4 per vehicle for 48hrs of diagnostic time. Still looking though. . . . .
http://repairpath.com/repairpath/subscription.asp