The Heat Genius system uses the Z-Wave wireless mesh network protocol to 'talk' to the devices that are placed around your home.
A mesh network is one that is robust as it can use 'listening' devices (i.e. devices that are always powered on) to relay messages around the network. (The listening devices essentially act as signal boosters).
The more listening devices that are present on the network, the 'stronger' and more resilient it becomes. If one listening device gets switched off, then an alternative nearby device can be used to relay messages instead.
Heat Genius use 'Smart Plugs' as listening devices to ensure good communications around larger properties. Smart Plugs can also be controlled from the Heat Genius system on a timer schedule, or overridden 'on-demand'.