By sending out clicks via the iPhone’s speaker and then measuring the time it takes to return to its microphone, Sonar Ruler can give a pretty accurate reading for how far a certain object is.

Clearly this is not going to be much use to people measuring anything other than walls or particularly large objects, but that said, its still pretty incredible. Watch the video here and try and resist downloading it…I couldn’t. (iTunes link)

Sonar Ruler Demo from cc laan on Vimeo.