Several years ago I wrote a Delphi IDE plugin to extend the functionality of the “Evaluate and Modify” dialog as well as the Watches window called dzDebugVisualizer and even released an update for it. Back then I wasn’t sure whether I wanted to open source it or possibly commercialize it. I am now sure that the latter isn’t worth the effort, so I have made it open source under the Mozilla Public Licence 2.
You can find the source code on OSDN. And since I was at it, I also added support for Delphi 2009. To install it, get the source code, open the appropriate package, build and install it into the IDE.
For the description see the links to my old block posts.