It could stop you from booting if it was confused :

Actually, I think the comment made by the OP was that it couldn't do a flow based shutdown, but I'm too lazy to check right now.

The scenario I'm being anal about is Windows hangs while unattended and a problem occurs. Is the shutdown mechanism dependant on the software running for certain things?

Sorry for playing devil's advocate It seems like all of these solutions have their flaws. Time to google some more, and see where I can find one of these three (tms-200, aquaero, bigng) in stock and at what cost!