I was at this talk at Blackhat Amsterdam last year and recalled it when hearing about an app called Gyroscope.<p>Essentially gyrosocopes can be used to pick up speech vibrations and therefore can become lousy microphones. The point is microphone access requires permissions, yet any app can have gyroscope access without permission.<p>Props to Yan Michalevsky, GabiNakibly and DanBoneh for an interesting paper and talk.