Seeing around corners, in the dark, and through smoke is difficult without specialized sensors[Velten et al. 2012], and so far impossible with a mobile phone. We use an active audio system to sense objects around occluders. Current techniques perform passive localization of sound sources with a microphone array, however, we demonstrate that with one microphone and one speaker pair, such as the ones found in mobile phones, it is possible to sense the specular reflection of silent objects such as mannequins around occluding objects. We demonstrate this technique by sensing a mannequin occluded by a wall.

More information here: http://dl.acm.org/citation.cfm?id=2614282