Even if they can dynamically track the receiver and use beam steering on the transmitted ultrasonic energy. How does that work in their coffee shop example? Do they need to dynamically track and steer multiple beams for every coffee shop patron? How tightly could they form the beam? If you have the phone on your ear or in your pocket, what leakage&#x2F;side lobes are directed at your body.
I know that ultrasounds are used medically, but there are power limits to prevent tissue heating&#x2F;cavitation. If they want to deliver 5-10W at the target what about someone standing in a sidelobe closer to the transmitter. How quickly can they shut off the beam from going right into your ear if you move the phone away from your head?