Ping))), the ultrasonic sensor (also known as Sonar) from Parallax is a must have for your programmable robots Boe-Bot, Sumobot and StingRay. This ultrasonic sensor is able to measure distances from 2cm to 3m. This ultrasonic range finder consumes little power and offers a relatively narrow cone of detection.
Video presenting the Ping))) ultrasonic range finder:
The following image decribes the general operation of the Ping))) ultrasonic range finder