Rated 5 out of 5 stars

Excellent addon, and the only one of its kind that I've found. The newest version (found in the all versions section) has an entirely new interface that not only looks better, but makes it easier to select elements of a page to watch for a change. Highly recommended.

This review is for a previous version of the add-on (0.4.9.20130722.1-signed).  This user has 2 previous reviews of this add-on.