PacketTrap gives enterprise 'Perspective'

Here is where the real magic happens. These alerts allow you to pick a condition to look for, what it should do should it see that condition occurring, an escalating factor of if things are getting worse, and then a final resetting condition which once it hits that, it'll reset the alert.

You can set it to alert the administrator or anyone else in the organisation. You could even set multiple triggers - if disk usage gets too high and network usage is too low, something is obviously screwy and needs looking at.