The ‘Press power button twice for camera’ gesture was an awesome feature of Nexus 5X and Nexus 6P. This lets quickly open camera without unlocking the screen. Now, Google has implemented this gesture on older Nexus devices, such as Nexus 5, Nexus 6, Nexus 7 (2013) and Nexus 9 with the new Android 6.0.1 update.
The new Android 6.0.1 update (build MMB29M) has already been released with few new features and security patches. As said above double click power button to open camera is one new feature for older Nexus devices and the settings for this gesture can be located under display settings menu.
The quick launch camera gesture is certainly a very useful feature for capturing something quickly, though there were few glitches. For example, the power button double click should be instant, otherwise will open the screen and ask for security pin.
Besides the quick launch camera gesture, the new Android 6.0.1 update (build MMB29M) brings lot of new Emojis, improvements in the navigation bar, ‘Until next time’ option for Do Not Disturb, bug fixes for washed out colors in Nexus 5X and latest (December) security patches.
You can download the factory image [HERE] and flash it manually [Instruction here], or you can wait for the OTA update to hit if you wish to avoid a data wipe on locked bootloaders (Source 1, 2)
