Nexus 5 (or any other 4.4 device) - How to add NiLS widget to the lock screen

Simply check Android Settings > Security > Enable Widgets, and continue follow instructions as guided on NiLS app itself.

(Thanks to GottabeMobile.com for the screenshot, full guide here: http://www.gottabemobile.com/2013/11/11/add-lockscreen-widgets-android-4-4-kitkat-nexus-5/)