It allows you to tag in and out of the house for those times you don't want to fiddle with the keypad on the Nest Guard. Nest executives stress that the 1. 46 inch circular Nest Tag is pretty durable, capable of surviving a trip through the washing machine if you forget to remove it from your pocket. In addition to the keypad on the Nest Guard and the Nest Tag, there's a third way to arm and disarm the system — an app on your phone. The app will even send you a reminder to remotely set the alarm when you leave the house. The app's also where you'll get security alerts whenever the alarm goes off. Nest Detect, attached to a doorNest executives say they designed the Nest Secure system with the people who live in a home in mind as much as the burglars trying to break in. That approach is readily apparent in a feature that allows you to set how much time you have to leave the house before the alarm is set. The Nest Guard will give you an audio alert too, telling you how much time you have to get out. While the Nest Guard plugs into a wall, it also features a rechargeable onboard backup battery that gives you 12 hours if the power ever gets knocked out. The Nest Detect runs on a CR12A battery that promises two years of battery life.