Show number of new posts on dashboard

Stackexchange, facebook, and a number of other big sites have a very useful feature where they show new notifications in a small but conspicuous red icon at the top left of the site:

I would find something similar for posts drupal.org very useful:

I would propose that the number shown is the number of posts with new replies since the last time I visited my dashboard or tracker. The dot should probably link to the "Your posts" page, just in case the widget isn't enabled on my tracker.

Note: on facebook and stackexchange, the dot actually has a drop-down with links to the posts themselves. I think this is unnecessary, at least in the short term, and a simple notification is enough.