Well, really, just about any of them will allow you download the software for free, but the software wont work without their hardware in most cases. With that, most of the major scan tool vendors have software that will work with laptops especially and some with PDA's. AutoTap is one that does. Just be sure that the scanner you get has GM enhanced parameter capability or you will not be able to monitor for KR. If you want to do a bit more research, check out the links below.
Check Engine Light OBD2 OBDII scan tool OBD
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AutoEnginuity® - OBD2 Scan Tool - Professional PC and PDA Diagnostics
AutoTap - OBDII Diagnostic Scanner
AutoXray®
