However dubious you are about the science backing up On/Off's paint, you can't argue against its sheer innovation. Suitable for all surfaces, it lets you control the lighting with just a touch and can even be covered over with wallpaper.
That touch can be anywhere on the wall, or if you'd rather keep the light switch confined to just a strip running at mid-height on the wall, that's possible too. It could be useful in children's rooms, or as DVICE suggests, all over the house for drunken fools. [APCI via PSFK via DVICE]