A compass attached to a car door mirror is disclosed which provides protection for the compass and improved readability, while avoiding the reliability problems of compasses mounted inside the car. The compass is embedded in the frame of the car door mirror which makes it both less obtrusive and physically...http://www.google.co.uk/patents/US4581827?utm_source=gb-gplus-sharePatent US4581827 - Car door mirror equipped with bearing magnetometer
