But, as they say, it may be a bad idea to put all the eggs in one basket, so, if you go the multiple units route, even if it’s a more costly solution, in case the smoke detector fails, you’ll still have a CO alarm and vice versa. If the 3 in one detector fails, usually, all sensor will stop functioning. It is possible for you to find a functional smart smoke detector for $50; however, most homeowners want to spend more on key features as well as a boost in quality. If you want your smart smoke detector to include a carbon monoxide alarm, then expect the cost of your purchase to go up quite a bit. A CO2 detector is essential if you don’t have a separate one. Also, it is important that you remember the fact that you will be purchasing a smart device. 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.