To some degree, the best "monitoring software" doesn't even monitor at all - it simply provides a framework for people to add their monitors to. To take one example I'm familiar with (though I'm sure this could be applied to the rest of the great monitoring systems) - Nagios is, at it's heart, a State-Tracking/Notification/Scheduling Engine. The fact that you can add commands like "ping" or "http test" or "Database Schema Verification" to the tasks that you are scheduling and tracking the state on, is almost incidental to the core of what Nagios does.
I agree completely, and I think Nagios does a good job at state tracking, notification, and scheduling. The interface is a bit clunky, but with the nuvola makeover it's completely serviceable. Pair it with something like ganglia or cacti for visualization and you're most of the way there.
