I don't think I've ever seen something like the Philly Fountain. Of course, that's not surprising since it's still just a concept conceived for the city of Philadelphia.
Designed by Justin Johnsen, the Philly Fountain features a solar-powered touchscreen that encourages social interaction. Basically, you can draw on it then passersby can elaborate on your artwork. The Philly Fountain also glows to indicate its presence at night.