HMC1021S Honeywell, Unipolar Magnetoresistive Sensor, 8-Pin

Magnetoresistive circuits, single axis and double axis comprising a Wheatstone bridge with 4 magneto resistive branches
Create a compensation field to eliminate an unwanted field (offset+, offset-)
Can be re-initialised in the event of drift
Measure movement or angular or linear positions
Highly sensitive - can detect the Earth's magnetic field
Minimal hysteresis and background noise
Typical uses: electronic compass, vehicle position monitoring, virtual reality etc.

Magnetoresistive Sensors, Honeywell