A new research paper (http://tinyurl.com/p96ytfp), by Disney Research and Carnegie Mellon University, details how ultrasound from a smartphone can be used to help form a physical input device. A plastic sheath for the phone contains a tube connecting to the microphone and speaker; sound travels through the tube and deforms it to act as a passive input device. The sheath holding the tube can take many different forms, and can be 3D-printed, the paper says. For instance, it could serve as a combined stand and control mechanism for a smartphone serving as an alarm clock. There are no plans to commercialise the technology yet.