This application uses a proximity sensor and lock/Unlock a terminal.  
Convenient for the flip type cover. 
When dark colors, such as black and brown, are being used with flip covers, such as Galaxy Note, a proximity sensor may not react. 
In that case, it may be improvable if the sticker of white or a bright color, etc. are stuck on the portion in contact with the proximity sensor (upper part of a screen) of a flip cover. 
This application is using DeviceAdministrator.
So it is necessary to cancel at the time of uninstallation. 
(Other settings => Disable DeviceAdmin)
This application uses the device admin.
This is used to shift the terminal to the lock screen.