The FS20 system by Conrad is a simple RF-based set of modules to turn various appliances on and off. The transmitter looks like this:
The most basic on/off remote control switches are as follows, shown with central European power plugs:
They have an on/off toggle on the unit, which is a big plus over simpler units. The other useful aspect of these units is that they operate over the 868 MHz band, and that the details of the FS20 protocol are available. Several projects exist which can receive and/or transmit the corresponding signals.
Definitely not the most beautiful design, but hey, they get the job done…