WebSentinel!

Distill is a web monitoring tool. It can monitor RSS feeds, a webpage or a part of webpage. Alerts in the form of pop-up, audio or emails can be received.

Update Scanner is a Firefox extension to monitor web pages for updates. Useful for websites that dont provide Atom or RSS feeds.

Stays in the background and monitors web pages for changes.This extension allows your browser to monitor changes to web pages for you. It can inform you whenever a particular page changes without you having to go and check every time.

Web page and json monitor, is an extension for the most modern browsers, It is used to monitor any Web page, such as a price at Amazon; A search on Google or more commonly where an RSS feed service is not guaranteed