Gesture sensor when in pockets and battery utilisation of the sensor

[nickthorley]

I like the look of some of the gestures on the S4, particularly the swipe to check notifications. However I wondered how much of an impact on battery life this has with the sensor having to be constantly monitoring.

Also how do people go on who keep their phone in their pocket when walking around. The body would then be in constant contact / in front of the gesture sensor and hence does the phone keep activating and draining battery life or can it tell the difference between a quick gesture and a body in permanent contact?