We have successfully using an Ethernet DIN Relay switch in our open-pit mine monitoring systems.http://www.digital-loggers.com/din.html
In principle, the unit can receive a command over Ethernet, which can tell it to turn off the power to a device attached to one of the 8 power connections. The power supply can then be restored with another command.
It's a simple job (so I'm told!) to write a small piece of software to connect to the device; alternatively, you can log in to the built-in web server and switch devices off from there.
Hope this helps,