[mythtvnz] FrontEnds Controlling Audio Mains Power

[Tortise]

http://www.voltelectronics.co.nz/power/energy-saving-products/new-usb-sensing-mains-power-switch-kit.html

Actually these are available, and seem to elegantly do it, for a price....   Of course the BIOS would have to be configured for USB 
keyboard power on off, otherwise the switch would probably not work.  I also note the PS2 sockets have a 5V rail (>200mA) which 
almost certainly will switch, so that's probably another way to get a signal, I imagine PS2 would work with this kit.  Also from 
what I can tell it seems this kit has two control options, one is the 5V USB rail and the 2nd is the USB line, which suggests 
software control might be also be an option.