Smart Lock automatically unlocks the device when trusted locations (work, home) or other devices (Bluetooth® headset, NFC tag) have been detected.
A secure lock type (PIN, pattern, etc.) must be configurar for Smart Lock to be available. Turning off the secure lock also turns off Smart Lock.
From a Home screen, navigate: Settings > Lock screen.
From the Screen security section, tap Smart Lock.
Enter the current unlock method (e.g., PIN, pattern, etc.).
If prompted with 'What is Smart Lock?', tap GOT IT (lower-right).
Select any of the following available options then follow the onscreen prompts to set up a trusted unlock:
For more info on Smart Lock (editing, removing settings, etc.), refer to this Google™ support page.
On-body detection: Keeps your phone unlocked while you're carrying it on you (pocket, purse, etc.).
Trusted places: Set locations (home, work, etc.) to keep your phone unlocked whenever you're there.
Trusted devices: Set Bluetooth or NFC devices to keep your phone unlocked when that device is connected.
Voice Match: Unlock your device using voice recognition.