Crownstones can make power outlets and lights a bit smarter. The small units are placed behind the outlet or behind a ceiling light.
Crownstones make it possible to have devices or lights turned on or off depending on the presence of a phone. When from the viewpoint of the phone four or more Crownstones are in sight, then it is possible to determine in which room someone resides.
With indoor positioning it is possible to turn on lights exactly on the moment that it is getting dark AND someone is present in a particular room in the house.
Flows can be used to also control other devices using information about the presence of people.
The physical space behind a power outlet or ceiling light has to be sufficient for a Crownstone. For indoor positioning it is important that at least four Crownstones are present. The positioning makes use of Bluetooth LE on a phone (if there's no phone carried on or if Bluetooth is turned off, there is no positioning).
It is possible to use a Crownstone simultaneously with a physical wall switch. See Crownstone support for how this has to be configured.