Advisory Check is a program that reads security advisories for you. It gathers security advisories using RSS, RDF, or XML feeds, compares them against the installed software, and alerts you if you're vulnerable. A wide variety of package managers can be queried to detect installed software. Remote systems can be monitored by using the integrated SSH, Windows-RPC, and Nmap support.
BigDaddy is a program for monitoring servers. It is similar to Nagios, with the added benefit of also monitoring and controlling the crontab (or any scheduled application) across an entire fleet of servers. The application comes in the form of a daemon for monitoring and reporting as well as an easy-to-use Web-based GUI for controlling monitoring, viewing timelines of incidents, filing incidents and graphing statistics. The application is extensible with any sort of monitoring module and notification is based on a five step escalation process.
Daedalus provides a simple mechanism for running programs in response to the output of "check programs". In practice, this is generally used to provide an automated restart service for programs by checking the output of "ps axww", and running a start script when a particular program fails to appear. However, it can be used for any occasion where you want to automate an action based on an event in the system. Beyond simple restarting of systems, it can be used to send alerts, clean up files, or even start one program when another finishes or reaches a certain point.