Serious Hacks Possible Through Inaudible Ultrasound

“High-frequency audio ‘beacons’ are embedded into TV commercials or browser ads. These sounds, which are inaudible to the human ear, can be picked up by any nearby device that has a microphone and can then activate certain functions on that device. But the technology has many more applications. Some shopping reward apps, such as Shopkick™, already use it to let retailers push department or aisle-specific ads and promotions to customers’ phones as they shop.”