This video shows the simple use of the PING))) sensor to detect the distance an object is away. In this case an LED lights up when something is placed within 3 inches of the unit. The can be expanded upon in many different ways for navigation and proximity detection.
This video shows the distance measurements (converted to both inches and centimeters) being displayed on the serial monitor screen and changing as a box is pushed towards it. While currently it is only being displayed on the computer via USB, it could also be done using an LCD screen or writing to an SD card to make it completely mobile.