I have been working on a sequence diagram for the simple uml plugin for several months. Kesha's modification to it finally caused me to finish it up so that I could distribute it. He was kind enough to send me his modification so that I could release for both Aurora and 3.1. This implementation began with Alex Moffat's standalone sequence diagram program as well as Martins plugin and then built up. Here are some of the basic features:
1. Added the ability to click on the links to navigate through intellij
2. Added the ability to add directly to the diagram from intellij via Alt-A (Add) while selecting a method name. The diagram does its best at determining where this call belongs on the diagram.
3. Added the ability to add return statements via Alt-R (Return)
4. Added the ability to produce design documentation. I did this by adding java doc information into the model file (]]>.suml) which is XML. The program then applies a stylesheet to generate documentation that will accompany the diagram.
5. Added the ability to place comments on the diagram.
I know this isn't perfect and there are probably many bugs but I have found it useful and hope that you do as well. Thanks to Kesha and Martin for their excellent contributions.