In a presentation at the Usenix security conference next week, researchers from Stanford University and Israel’s defense research group Rafael plan to present a technique for using a smartphone to surreptitiously eavesdrop on conversations in a room—not with a gadget’s microphone, but with its gyroscopes, the sensors designed measure the phone’s orientation. Those sensors enable everything from motion-based games like DoodleJump to cameras’ image stabilization to the phones’ displays toggling between vertical and horizontal orientations. But with a piece of software the researchers built called Gyrophone, they found that the gyroscopes were also sensitive enough to allow them to pick up some sound waves, turning them into crude microphones. And unlike the actual mics built into phones, there’s no way for users of the Android phones they tested to deny an app or website access to those sensors’ data.