This is so simple. You plug your PC into the main socket, and then plug your printer, scanner, monitor etc into the other sockets. When you turn off your computer, the smart unit shuts the power off to the other sockets. Saves power from constantly-on transformers, saves the environment, and saves lives from electrical fires caused by overheated DC adaptors. Also works for AV equipment.
Smart Strip Power Strip, $31
Available from Amazon