This means you will be given alerts of possible fires even when you are miles away from home. This makes your purchase a bit costly if you get one that’s reliable. "This battery operated device sells for $199, and communicates with your smartphone via Bluetooth," said Nerds on Call. "When the Smart Lock identifies your Bluetooth signal approaching, it unlocks your door, and can lock it behind you if you choose that setting. It also allows you to set up virtual keys for guests, with the ability to grant access for only certain dates and times for each key. The activity log keeps track of when each unique user comes and goes.