Hostgroup Percentage


I am setting up Nagios as the monitoring system for a mid-size network (~2,000 devices).

I have the equipment broken down into hostgroups based on what site it is located at. I am trying to figure out how to only send a notification if a certain percentage of the equipment in a hostgroup is down/unreachable, say 30%.

I guess I need a check_hostgroup plugin. Anything like this exist? Any other ideas??

Thanks in advance!!