Inside [Klaus]’ device is an Arduino Uno, an HC-SR04 ultrasonic distance sensor, and an Adafruit Wave Shield.

Specifications of the ultrasonic sonar distance sensor that can be used with Arduino, Raspberry Pi, CircuitPython and more include : – Power & Logic Voltage: DC 5V – Current during measurment ...

With a standard old HC-SR04 ultrasonic sensor, an audio module and a servo to drive a custom gauge needle he’s made a device which can warn people around you if they’re too close for comfort.