Specto is an excellent little Python script that monitors all manner of events, and then notifies you of any changes. It's a lightweight alternative to the usual heavy-duty, complex network and system monitors, such as OpenNMS, Zenoss, Zabbix and MRTG. Specto does not replace these, but provides a useful alternative when all you want is to be notified when something changes.
For example, you can set Specto to monitor your Web site. Then, if the site goes down or gets cracked, you'll know right away instead of suffering the embarrassment of hearing about it from someone else. You can set all kinds of targets for Specto to monitor: e-mail folders, files and directories, system processes, forums, blogs, and Wikis.
This is a flexible system that you can adapt in many ways. It's a quick and easy way to watch logfiles. It's also an easy way to monitor forums and Wikis for spammers and trolls, and other new entries. It will watch for new additions to version control systems.
Specto is included in most Linux distributions, including Fedora and Debian. It sits unobtrusively in your system tray, then emits a dignified popup when a target changes. After you have entered your watch targets, they can be de-activated and re-activated easily, so you don't have to hassle with deleting and re-creating them as needs change. The refresh interval is invidually configurable for each target. Visit Specto for more information and screenshots.