Martin is talking about reverse trackbacking (in german), i.e. a method to have your own blog pinged when you’re commenting on someone elses blog.
In his prototype application, you can enter a URL you want to have pinged. In an ideal world, this would come through some kind of identity management architecture after you identified to be able to comment.
Excellent idea. Francois, are you listening?
Btw.: I was just trying to find a URI that I could trackback to point Francois Planque, author of b2evolution to this post. I can’t do that without refering to an explicit blog post of his – maybe every blog should also have a “do you want me to notice this?” URI for post un-related trackbacks.