Web Content Monitor (WebEx) автор Ayukawayen

Web Content Monitor is a tool to periodically track information on web pages.

To add a web content to monitor, right-click on a web page and click "Monitor Content" on menu, then select monitoring area.
The update interval and notification type could be set individually for each content. The add-on will fetch content values automatically in background, and the latest values of each tracked information will be shown in the pop-up panel.

Android Version (BETA) is available on Google Play. Now you can monitor contents on your Android smartphone:
https://play.google.com/store/apps/details?id=net.ayukawayen.infotracker
(Data or setting do not shared between Firefox Version and Android Version.)