If your Android's power button is broken then this Volume Button for Power Button is for you!
#Power Button issue Fixed by unlocking with Volume Button for Power Button - -Unlock by volume button
With this really nifty app running on your Android, you can use the volume button instead of the power button to wake up your device! You can Unlock screen without power button.
IF YOU WANT TO UNINSTALL THIS Volume Button for Power Button Unlock by volume button go to Settings > Security > Device Administrators and remove the app from the device administrator list. Then you will be able to unable to install the app as you normally would. If you are wondering why the app was on the administrator's list to begin with, it's because only apps that are device administrators can turn on and off the screen. You actually opted-in to this, but probably didn't bother to read the relevant messages when the app asked for this permission...
Please note that you may experience a power drain on the battery. This comes with the territory of keeping your device awake at all times in order to enable the volume button to perform the power button function. With recent updates to the Android operating system - this is the only way to do it.
If this app is run without the screen off setting, then the long term behavior of this app becomes unpredictable, as it is subject to the operating system's whims to reclaim memory. We recommend that you enable the 'screen off in notification bar' feature if you plan to use the Volume Button for Power Button for long periods of time.