It seems to be a ceiling light with a switch that controls it wirelessly, rather than with a cable looped in. Why isn't that used more? I'm looking at some major electrical rewiring, and this would save an awful lot of chasing out the walls to drop the cables down to the light switch. Compared to the cost of chasing, making good, and redecs, this is only £15.
What am I missing? Why isn't this done routinely, even for new-builds?