CentOS - Feb 2006 - slightly OT: high availability remote managerment tools

This is completely OFF TOPIC from centos and slightly vague, so please reply to
me
direct. I just want to pick everyone's brains here for their experience with
high
availability remote management (servers, networks, etc).

Can anyone recommend any good high availability remote managerment tools. I mean
something more than ssh, nagios, etc. Anything from appliances to monitoring,
remote
access, be it software or hardware.

Thanks in advance.

Dustin