Lumens auto screen locker

Lumens is the measurement of light. This app takes the average ambient light and uses it to detect user action.
Lumens Locker / Unlocker is a smart locker that is able to detect if the phone is on your pocket, facing down, inside your bag or covered with phone case.
This is through the help of Accelerometer and light sensor. This is great for phones with damaged power buttons or if you don't want to wear off the button or you want to feel like a magician or you're simply just plane lazy. Lumens locker saves you the hassle of reaching for the power button.
Tweak the app to your preference.

Limitation: light locker will not work if the average ambient light drops below 10 lumens. it will use proximity detector instead.

Premium vs free
Premium extras:
Vibrate customization
Unlocking while upright
Ad free

If it doesn't work with your device please drop me a mail of the phone model first before flaming on Google Play Store. Accuracy will depend on the phone manufacturer. Sometimes manufacturers lessen the light sensor accuracy/sensitivity to "save" battery. Based on my observation, the recent Samsung devices has the best accuracy in light detection.

Tested on devices:
Galaxy nexus
Samsung note 3
Xiaomi mi3
Htc one
Samsung nexus tablet 10