One project which I am working on is getting mochitests to run in fennec + electrolysis. Why this is a project is we don’t allow web pages to access privileged information in the browser anymore. Mochitests in the simplest form use file logging and event generation.
The communication channel that is available between the ‘chrome’ and ‘content’ process is the messageManager protocol. There are even great examples of using this in the unit tests for ipc. Unfortunately I have not been able to load a normal web page and allow for my extension which used messageManager calls to interact.
I think what would be nice to see is a real end to end example of an extension that would demonstrate functionality on any given webpage. This would be helpful to all addon authors, not just me:) If I figure this out, I will update with a new blog post.