Bryon,
Vikram is correct. The method I provided should only be used in a worst-case scenario. If you are using SNAC you could accomplish a clean shutdown (I think) by again a special group with a policy that goes something like this:
If process x (somethign you know to be running) if active,
Then run executable to shutdown the system. You could easily deploy the psshutdown (or other utility) ahead of time and call that executable.
Best of luck