From Perform action based on load avg it appears that Monit will do what you are asking.
You'll want to follow the steps at Resource Testing and use the LOADAVG(5min)
As an example:
if loadavg(5min) is greater than 4.00 for 2 cycles then exec '/usr/local/bin/frmwebkill.sh'
Where frmwebkill runs the command you specified to find orphans and then kills the found processes.