Mountain View, US (BBN)-Google is currently working on a new smart lock mode called 'on-body detection'.
This feature, senses the touch or the movement of the user, that is, when it does not trace any motion it locks the phone automatically, reports The India Today.
Once you unlock your phone, it will stay unlocked while you're holding it or it's in your pocket.
And when you set it down, it will lock again.
The idea being, if you leave your phone sitting on a table or forget it somewhere, it will lock, preventing would-be thieves from easily accessing your data.
So, clearly, it requires manual unlock by the user when the device is picked up from a static state.
However, if you hand the phone to someone else while it's unlocked, it will stay in the same mode and not lock, that is, the feature is not able to recognize the user's specific touch.
It just knows when the phone is being held/pocketed and when it isn't.
This feature was noticed on a Nexus 4 running on Android 5.0.1, but we're now seeing it on many devices, with major percentage being of Nexuses.
However, this doesn't seem to be a feature related to Android 5.1, but you probably need 5.0+ for it to work.
The feature does not seem to be a part of the core OS and will probably be added separately by Google.
BBN/SK/AD-22Mar15-4:50pm (BST)