Android smartphones will lock themselves when they are not in the user's hand or pocket, early adopters of the " on-body device detection " feature are finding.
As described on AndroidPolice.com, they can choose not to lock the device when it is held in their hand or remains in their pocket or bag, but only when it is placed somewhere, such as on a table. They clarify, of course, that the device does not acquire the ability to recognize that it is the owner of the device.
When used unlocked and changed hands, it will remain unlocked. What the device can leverage when the On-body detection is the measurements of the acceleration sensor and perhaps other sensors, such as the proximity sensor, according to the first, unofficial estimates. Thus, it is able to distinguish the difference between holding/carrying the device and placing it on a surface.
On-body detection is part of the Smart Lock feature in Android 5.0.1+. Another option in Android 5.0+is to automatically lock your phone when it is in a pre-selected "Trusted Places" area.
Source: tech.in.gr
