Compass.magneticHeading
var magneticHeading: float;
float magneticHeading;
magneticHeading as float
Description

The heading in degrees relative to the magnetic North Pole. (Read Only)

The value in this property is always measured relative to the top of the screen in its current orientation. The heading of magnetic north is not exactly the same as true geographical north - to get the exact heading, use the trueHeading property.
    function Update () {
		// Orient an object to point to magnetic north.
		transform.rotation = Quaternion.Euler(0, -Input.compass.magneticHeading, 0);
	}