Easy Lock
Add double tap to sleep feature in your Android devices.
Using this app, you can double tap status bar / navigation bar / lockscreen / notifications shade to quickly lock your screen. No need to reach for the power button always!
Double tap status-bar to lock no longer works in Android 8 and above (limitations imposed by Android itself). However, double tap anywhere or double tap homescreen to lock options are available.
Source Code
Source code available under Apache v2 licence.
Download
Download can be found in the XDA page.