keyestudio SR01 Ultrasonic Module V2 is a very affordable proximity/distance sensor that has been used mainly for object avoidance in various robotics projects.
It essentially gives your Arduino eyes / spacial awareness and can prevent your robot from crashing or falling off a table.
It has also been used in turret applications, water level sensing, and even as a parking sensor.
This simple project will use the SR01 ultrasonic module V2 with an Arduino and a processing sketch to provide a neat little interactive display on your computer screen.