How to set up Nest Tag
To use Tag to arm and disarm Nest Secure, you first need to add it to your account in the Nest app. Then you can assign it to yourself or another person who has shared access to your Nest home.
You can always arm or disarm Nest Secure with your phone or by entering your passcode on Nest Guard, but with Nest Tag you simply hold it on Guard. There’s no passcode needed.