Check out the latest version of the lights-out WHS Add-in, which now has the possibility to check for CPU load and Network Activity. With the lights-out client utility it is possible to automatically wake the WHS when you need it, so it isn’t turned on all of the time.
By forwarding UDP port 9 to your WHS on your router it is even possible to wake the server automatically remotely!
Forum: http://forum.wegotserved.com/index.php?/forum/89-lightsout/
More Info: http://addins.home-server-blog.de/verwaltung/lightsout/#en