I remember reading an tutorial on how to use a cordless doorbell to turn your computer on, I cant remember the site though.

The problem with turning a computer on is there needs to be a voltage present and therefore cannot be done with software like a shutdown.

Might be worth checking out the link above from IRTrans as it seems the perfect solution, other than modifying a cordless doorbell and having your computer turn on every time someone's at your door!

Potato