Google appears to be quietly rolling out a new addition to the Smart Lock Feature in Android Lollipop, bringing an extra unlock option that works with motion sensors inside Android devices. “On-body detection” is designed to use your phone’s accelerometers to figure out when it’s been set down on a surface, and lock — with whatever lock pattern or PIN code you’ve set — when it’s not on your person.
The new feature is only available to Lollipop users, though you don’t have to be on a stock ROM in order to get it. However, activating it does seem to require the latest Google Play Services version, 7.0.97.
Using the accelerometer of the phone, the feature can figure out when you are holding the phone or have it in your pocket, and lock it when it is away.If you unlock the device once, it will stay unlocked till you are holding it or keep it in your pocket. Once you keep the phone away, it will lock again; while picking it up again will require you to manually put in the passcode.
Whether you should actually use this kind of feature is another question entirely. It’s potentially much less secure than tying your lock screen security to a Bluetooth device on your person, or simply keeping a passcode on at all times. It is perhaps preferable to no security it all, though, and Google’s probably targeting those who wouldn’t normally bother with lock screen security with on-body detection. Nevertheless, it’s far from an iron-clad defense for your personal data.