Can you elaborate on this? What exactly would you like to monitor?Can we make a feature request for monitoring Nagios processing?
Currently, you will be able to see the "first signs of trouble" just by looking at the system status page... It would show you if the performance grapher is running or not. If all of the dots below database maintenance are red, this would indicate that (most probably) crond is not running, which will also cause issues with graphing as perfdata files will be piled up in the "/usr/local/nagios/var/spool/xidpe" directory.
Is there anything else that you would like to see implemented?