SAPCompare is out! Check it out here. It's a Comparison tool for ABAP Object Classes and it can compare all the classes in two different SAP systems using RFC connection. Just goto transaction SM59 in your SAP GUI and set a RFC destination to connect to the other SAP system and just run the report. That's it! Give the classname and the RFC destination, it'll compare the whole system's classes all along with the private, protected sections and the method code.
The enhancement for integrating Webdynpro ABAP components is also written now, and I have found it to be even more accurate then the comparison screen they give in the version management screen. I am changing that code for enabling plugin development, so I should have that ready in a few days. Check back again after some time to read on about Wendynpro plugin development..