It will be interesting to know what kind of integration is planned for Nagios as it already supports Event handlers[1] for executing script when there's a state change.
[1] http://nagios.sourceforge.net/docs/3_0/eventhandlers.html
[1] http://nagios.sourceforge.net/docs/3_0/eventhandlers.html
In a way, neptune is your virtual first-level on call engineer. If we can resolve alerts for you automatically, neptune won't bother you. If action fails for some reason, it's escalated automatically to right on call engineer.