shutting down a process as part of the shutdown procedure

Is there a way for the shutdown procedure to have a script gracefully shutdown background processes and not proceed until it receives a reply? I need this to be done automatically when a server needs to be shutdown because a UPS's battery is almost out of power. From what I have read, OS X sends kAEQuitApplication to background processes but does not wait for a reply. I am currently running 10.3.9 but will upgrade if necessary. Thanks