Remote turn on PC computer Wake on LAN

http://www.raymond.cc/blog/archives/2007/10/21/how-to-remotely-turn-on-computer-from-lan-and-wan/

Just use the subnet mask 255.255.255.255 and it’ll send the magic packet to the IP address and MAC Address that you’ve specified.
Make sure you configure your router to forward port 9 to the computer that you want to boot up otherwise it will not work because the Magic Packet can’t get in your network. Refer to PortForward.com on how to configure port forwarding for your router.
You must know the external IP address, MAC address and also the Port. The default port for WoL over the Internet is 9. Some use port 7. Enter the correct information, hit the “Wake Up!” button and it’ll send the magic packet to turn on your computer. I’ve tried it and it worked.
remotewakeup.com

Tip: There are some routers that supports Dynamic DNS. This is a very useful feature where if your IP address changes, you can still keep track of your current IP address. My Belkin N1 wireless router has this feature and it’s easy to configure. I only need to sign up with DynDNS.org, and enter the information in my Belkin router.