Smart lock feature by Google for Chromebooks now allows you to unlock your laptop by its own when your phone is nearby. All you require is an Android phone running lollipop a k a Android 5.0 and a Chromebook running Chrome OS v4.0 or later. Your phone will then communicate via Bluetooth to unlock your laptop.
Google first launched Smart Lock for Chrome last summer but the team announced that it is now available for rest of the Chromebook users. This functionality will allow you to log into your Chromebook without entering any password which saves a lot of time. It is also very secure since it prevents unauthorized users from accessing your data.