Via networked_performance, and amazing positioning system that uses sidewalk pattern recognition (by Jason Kaufman and James Sears from Gumspots):

GSPS: GumSpots™ Positioning System--by Jason Kaufman and James Sears--is a pattern recognition technology which can be used for a variety of location aware services. Their demonstration of GSPS lets you enter and view hidden data on city sidewalks. A user would take a photograph of the GumSpots with a cellphone and submit it to the GSPS service. The GSPS service would then determine the location and orientation of the image and return the image with extra hidden data displayed on the image. In this case the hidden data will be text as well as 'connect the dot' drawings. A user also has the ability to add hidden text by submitting a note with their image.

Why do I blog this? I like this kind of trick that uses an environmental feature for a new purpose, that emerges from the designers creative thinking of how he can fix a problem (i.e. doing positioning).