Demand Switches are installed into the fuse box. They eliminate electric fields by turning off the circuit they are guarding, when no current is flowing. Sleeping amongst electric fields is a health hazard.
When you turn off the last appliance (e.g. the bedside lamp), the switch senses that no electricity is used and disconnects the circuit in the fuse box, giving you and your family a safe night's sleep (of course, it works also during the day). When you turn your light on again, it re-connects within a 50th of a second.
The functioning of other appliances, like the fridge, is not affected, as they are not connected to the same bedroom circuit.
The Comfort 7 is the latest development. It is able to detect and tolerate a residual current flow, which makes installation much easier.
Demand switches from Gigahertz come with capacitors, filtering out the incoming dirty electricity.
Demand switches need to be installed (circuit diagram included) by a licensed electrician. Note that there is no category for the Australian Standard. For that reason, it is not possible to register for the standard.
Gigahertz demand switches have come out on top in tests by the German consumer's association. (2017)