xjnm is a java daemon that gathers numbers from arbitrary sources (e.g. cpu usage) and can store it on arbitrary storages (e.g. a jdbc database) for later analysis or react in arbitrary way to the data collected (e.g. inform an administrator by e-mail).
Monitoring tool with support to Websites, RSS, Webservices and Databases. Has notifications by email and RSS and you can access metrics like availability, latency and load time by a web-based GUI. Runs standalone with an embedded HTTP server.