Ultrasonic bracelet jams the microphones around you. You could thwart eavesdroppers with your wristwear.
Smart speakers and other microphone-equipped devices aren't supposed to listen all the time, but there might be a solution if you aren't willing to take any chances. University of Chicago researchers have built an experimental bracelet that uses ultrasonic broadcasts from 24 speakers to jam most microphones, no matter what direction they're in. The gadget takes advantage of non-linearities in its built-in amplifier to 'leak' ultrasonic noise into the audible range and render recordings useless.