1. A method for detecting magnetic interference in a mobile device, the method comprising: monitoring magnetometer sensor data generated by a magnetometer for a first time interval; detecting a change in the magnetometer sensor data for the first time interval; computing expected motion data that characterizes an expected motion of the mobile device based on the magnetometer sensor data; comparing the expected motion data with reference data; and deferring recalibration of the magnetometer when the expected motion data does not correspond to the reference data.