Strictly speaking, a Theremin uses a pair of antennae that act as capacitors in a specific R/C circuit. Looking at ...

Instead, it relies on an ultrasonic distance sensor to detect a hand (or foot) waved in front of the door. An Arduino Leonardo runs the show, sounding a buzzer when the ultrasonic sensor is triggered.

Arduino AI monitors noxious air bubbles via ultrasonic scans This one is an unusual smart home project, potentially - how to monitor a fish tank’s health with an AI-enabled ultrasonic sensor system.

SJEC-AICTE IDEA lab in collaboration with Department of Electronics and Communication Engineering (ECE) at St Joseph ...

For the physical feedback, Denver has made some vibrating boxes that you put in your pockets. An Arduino polls the ultrasonic sensors and provides feedback via the boxes. This completely frees up the ...