On this page, we list software or packages that may serve as alternatives to Munin. This is not to gather intelligence or encourage industrial espionage, but to present pointers to other solutions if Munin was not quite what you had in mind.
If you were looking for the sort of enterprise-class monitoring system that notifies you of outages, rather than the sort that keeps track of things over time and makes pretty graphs, here are some options. Note that most of these provide a mechanism for tracking history of service checks, and may use RRDtool as a back-end for this.