An Arduino rangefinder with an ultrasonic sensor and an I²C interface display by Jan Henrik. He wrote an instructables here:
The maximum rated range is 500 cm, the range is measured 20 times per seccond. It is Displayed on a lcd screen which is 20×4 chars big, it has a custom start message, and it can have a custom design while measuring. It will have a backlight LED and can run on every arduino, which has I²C communication. That mean you can run it on an Arduino nano, which is very small. It also requires 5V so it has to be a 5V version of an Arduino.