Unlocking Your Chromebook Automatically With Your Android Phone
If you have a Chromebook and an Android phone running Lollipop 5.0 or later, you can automatically unlock and log into your laptop when your phone is nearby.
This feature, currently in beta, is called Smart Lock and connects your Chromebook and Android phone (but not a tablet, sorry) via Bluetooth. To set it up, go to Chromebook Advanced Settings and follow the instructions to pair your phone with your Chromebook.
The first time after enabling Smart Lock, you will need to enter your password to log in as usual, but after that you can simply press the green button on the lock screen to log in.
Smart Lock took a few tries to find my phone, but now it works like a charm and is very handy as my Google password is ridiculous to type.
Unlock your Chromebook with your Android Phone | Google via PCWorld