A magnetic sensor has a magnet (30) and a magneto-resistive element (20), arranged on a substrate such that magnetic field lines through the magneto-resistive element are substantially parallel to a plane of the substrate. Movement of a movable magnetically permeable element (40) near the substrate is detected as it alters the number of field lines through the element. It can be more sensitive than devices arranged with perpendicular field lines, and can be easier to manufacture and integrate. Applications include analog pointers, pressure sensors and microphones. It can use magnets placed either side of the element to detect changes in size of a gap above the element. As the gap closes, less of the parallel oriented field passes through the magneto resistive element.