Bat Navigator
As a little side project, I am working at something I called the Bat Navigator. It is basically a pair of glasses with two piezo transducers (rudimentary speakers), one for each side, and some ultrasonic sensors. An Arduino microcontroller controls piezos and sensors, so that the user wearing the glasses can distinguish the presence of obstacles and their distances based on the sounds produced by the piezo transducers. I managed to navigate indoors without bumping into obstacles while testing an early prototype.