This is a great add-on. The only thing I would ask is the chance to put the sidebar list in alphabetical order rather than newest added first. If you end up with a lot of sites that you are trying to monitor, you may end up adding the same site twice and not be able to delete the copy. PLEASE!

Please, make so that this addon make a simple request (GET) to some user defined URL to trigger any user`s procedure (when a webpage is updated).

Works as advertised. Sometimes sites with very active side-bars can fool it, so the only feature I'd add is to be able to "train" it what sections of a web page it should care about.

looks pretty good