It's horribly, horribly complicated, and probably won't work at all in modern environments: WOW (or WOL) don't work over wireless connections at all AFAIK, and they are becoming the standard rather than wired.
Even wired, the problems are twofold: a shut down PC doesn't have an IP address, so you can't refer to that - you have to use the MAC - and the MAC address doesn't leave the local area network, so it doesn't go to the internet.
Having said that, it is possible, but will depend on your modem to a certain extent.
Have a look at this:
http://www.smallnetbuilder.com/lanwan/lanwan-howto/29941-how-to-wake-on-lan-wake-on-wan[
^] - it should give you some idea, but after that you are on your own - I've never tried, and probably never will! :laugh:
I suspect this is going to be pretty complicated...and a PITA to test!