One click to lock the screen, free your power key off your device.
The app is small (only 8KB) and efficient, it do one thing only, just lock the screen, it don't need any permission.
You can swipe up from the navigation bar to quickly lock screen over Android 4.1(Jelly Bean).
Uninstall method: Settings -- Security -- Device administrations, deactivate it then uninstall.
Turn Off Screen