autowol
automatically turns on a local computer when needed
At home I have a little PC that acts as a NAS and NFS server. This server is being used only once or twice a day, so it would be wasteful to keep it always on. I programmed the server so it shuts down itself automatically. I won't go into details how, since that's not the subject, I will only tell that it includes monitoring the TX counter of the server's ethernet interface.
The point is, that this server shuts down automatically, so whenever I want to access it, I need to, well, turn it...