This is a bridge for the Parallax Ping))) sonar. It returns distance as a raw 16 bit number. Uses the SPI in slave mode. The idea is to have the master only have to ask for different sensors (like the Ping))) sonar) for a value instead of having to deal directly with the sensor. This is ideal when using a lot of sensors. It also lets you connect more powerful micros to these sensor without having to worry about writing the low level code to deal with them.