The reason for this design is because existing MEMS devices (gyro/accelerometer/compass) don't define "YAW" the same as is done in the aviation community. This was originally designed for this "yaw detection" purpose and in fact works in conjunction with an Arduino microcontroller and a gyro/accelerometer board. No relays are needed in this case but could be used if desired. The project was listed on this site simply because it could potentially have uses outside of the original application. Its principal purpose is to provide a "skid" indication in an aircraft, but will work on any vehicle experiencing this condition during a turn.

@hek Thanks; maybe I'll try the inclinometer project.