The Fulgurator is an innocuous device that allows you to insert an image or text into any photograph by pointing it at the object being photographed. Though not visible to the naked eye, the text or image shows up on the picture.
Wired Article about the Fulgurator
Official Fulgurator site (via Google translator)
The video below shows the Fulgurator in action at Checkpoint Charlie in Berlin.
Okay, so it' not disability related, but its still very cool.