Nagios with MRTG or Cacti are pretty much the way to go. Once you get past the learning curve they aren't as complicated as they seem. You can trigger alerts via email/sms/pager based on just about any event you can imagine.
Those are also helpful in that they can attempt to restart dead services before getting you out of bed.
There are probably commercial packages out there that will do what you need, but I'm an open source guy.
Not really helpful, but that's my
