alt Hacker NewsTrivia time! The first practical wireless remote control for TVs also used ultrasound: https://www.youtube.com/watch?v=MLPk1Us62xQ
Trivia time! The first practical wireless remote control for TVs also used ultrasound: https://www.youtube.com/watch?v=MLPk1Us62xQ
Right, and they were superseded by battery-powered infrared remotes for good reasons. I would recommend revisiting those reasons before proposing this sort of technology for wireless sensors.