Super-sensitive, zero-inertia acoustic sensor...

Super-sensitive, zero-inertia acoustic sensor.  There aren't too many details, but enough to convey the basics.  Conventional acoustic sensors – aka microphones – all depend on movement of some part of the sensor.  This moving part – usually a thin diaphragm – has some mechanical inertia, and this is the limiting factor to its sensitivity.  This new acoustic sensor has no moving parts at all; it directly senses the motion of the air molecules as sound makes them vibrate.  Furthermore, it can be constructed to have directional response, which means that it can tell what direction the sound is coming from.  Right now it's used only in (very) expensive military applications – but if it's cost can be brought down, it could enable all sorts of interesting civilian applications.  For instance, it could let your mobile phone, sitting on the table in your kitchen, track you as you moved around the room and deliver your voice perfectly clearly.