But I was referring to editing the lock screen through the phone GUI, like in samsung devices or in my nexus 10.
Is there a way to add for example whatsapp missed messages indication to the lock screen?
Well widgetlocker(as far as i remember) does not actually allow you to add any widgets to the screen. just to customize the look. In android 4.2 you can add (pretty much) any widgets to the lock screen....and even if widget locker can have system widgets i would much rather android do it itself...avoids installing a 3rd party app that could be battery hungry...