These floor tiles have little LED dots embedded in to them. When you walk over the floor the lights come alive as foot prints. The lights will vary in brightness dependant on the weight of the person walking on the floor. Once you move from the floor the LED's gradually dim down until they switch off.
Walyou, the site where I spotted these cool tiles, suggests that a timer should be used to switch them off in the early hours of the morning as they would look a bit scary on the 3am run to the toilet. Also, walyou suggests they change colour rather then brightness so you can see if you are over or under weight.
The idea was thought up by LED-Emotionalize and unfortunately they just seem to be an idea rather then a product you can currently buy.