One of the banner features of owning a Lumia PureView device tends to be the dedicated camera button. It seems like a small thing, but once you start using one, it is hard to go back to just a software camera launcher.
A neat trick that Lumias like the Lumia 950 and Lumia 950 XL have enabled out of the box is a feature to prevent accidental camera launches when in your pocket. It works by enabling the front sensor near the earpiece for proximity detection. You can try it yourself by covering the top front of the display with your finger and then trying to launch the camera button ? it won't work.
Full story from the WindowsCentral blog...