This is already possible! I used my laptop, an interface & some 'still under development' software to diagnose why my injector light was on. Comparing the trouble code to the DTC list, indeicated camshaft angle sensor malfunction - when I lifted the rocker cover it was correct - in pieces all over the engine!
The software works on ECU's which use the KWP2000 protocols - the software has to be bespoke becuase FIAT's range of ECU's are finud on a different address to all other mfrs wink
So for simple DTC troubleshooting the answer is yes - dirt cheap - about £10-$15 for the electronics required to make up the interface to an rs232 (serial comms) port. And it works under windows, including NT based versions.
Currently it does not read real time values (I and a few others have experienced the same problem doing so with Alfa ECU's - a standard OBDII function not supported is the error returned)
It's only a matter of time before we crack it wink
Websites are like ********s, everyone has one, and im wary of any bloke trying to direct people into their's