Hints to Other Tools
There is an abundance of networking tools concerning monitoring, sniffing, and scanning. Two of my favorites are Cacti and Nagios. Cacti is a monitoring tool similar to Munin, but it seems more powerful. Nagios is a tool designed to monitor machines and services.
With Nagios you can not only determine if a server is still answering pings, but can also check for services by accessing them (using e.g. the samba or HTTP protocols) and trigger actions when the service is not available. You can have your Nagios machine send you an SMS if your OpenVPN tunnel is down, or if the management interface is not reacting.
