Two engineering students from London South Bank University in London, England have created a rug that glows in the dark when pressure is applied to it/it is walked on. Exploring luminescence (and creating glow in the dark footprints) is part of a college course they are studying. 

The rug they have invented uses electroluminescence, which works by passing a current through a material which emits a soft glowing light when electrified. The light is a recognizable green-cyan glow, as that seen in LCD wristwatches and thin film nightlights. The most commonly used medium used for these applications is a powdered phosphor.

The students have named their prototype rug the Footlume, and its principles rely on the same concept of powdered phosphor that is powered by rechargeable batteries.

This means that in addition to passive lighting uses the rug can also be set to flash in time with music, so it could potentially become a dance party rug, as well.  In addition to obvious home safety use, the home decorating industry has expressed an interest in electroluminescence in floors and walls for ambient lighting use and as potential replacements for some lower-watt electrical lighting requirements.

Read more here.