1. A method, comprising: at a time a mobile device enters a motion detection mode, turning on a proximity sensor of the mobile device and setting the proximity sensor to operate in a passive mode, wherein in the passive mode, the mobile device establishes a baseline of the proximity sensor, the baseline comprising a proximity reading indicating that the proximity sensor does not detect an object, the baseline usable by the mobile device to determine proximity with an object upon determining that proximity readings of the proximity sensor satisfy a specified offset from the baseline; obtaining a motion reading from one or more motion sensing devices of the mobile device during a time that the mobile device operates in the motion detection mode; while obtaining the motion reading, and prior to a gesture is recognized from the motion reading, acquiring a plurality of readings of the proximity sensor for establishing the baseline and establishing the baseline from the plurality of readings; after setting the proximity sensor to the passive operating mode, recognizing the gesture, including determining that the motion reading indicates that the mobile device moves towards a target object in one or more specified fashions; after recognizing the gesture, performing actions comprising: setting the proximity sensor to operate to an active operating mode; determining that a difference between a reading of the proximity sensor obtained in the active operating mode and the baseline determined by the proximity sensor before the gesture was recognized satisfies a threshold value; and in response, confirming that the gesture is not a false positive; and then performing a task in response to the confirmed gesture, wherein time taken to establish the baseline is masked by time during which the mobile device is in motion.