Smart Lock allow Google’s two computing platforms to work together, forming a trust relationship, and use that relationship to sign into your Chromebook without the need to enter a password every single time. As long as your smartphone is nearby, running Android 5.0 Lollipop, and unlocked, you can sign into your Chromebook with just the click of a button. From Phandroid - Unlock your Chromebook with Android 5.0 Lollipop’s Smart Lock