This program utilises master-slave communication (I2C). It uses two Arduino Unos, one being the slave, the other being the master.
The slave: Reads from an Ultrasonic Sensor (HC-SR04) to calculate distances. At a request from the master it splits the distance into two bytes, and returns them.
The master: Establishes the master-slave relationship and continually requests two bytes from the slave. While a button is pressed, it converts the distance to inches instead of centimeters. It outputs the inches or centimeters to a LiquidCrystal Display.
A picture of the hardware setup can be seen in the file: "hardware_setup.png".