The battery powered Google Nest Protect and Google Nest 3rd Generation Learning Thermostat have been designed to work together. When the Google Nest Protect detects carbon monoxide (CO) as well as sounding the alarm it also communicates with the Google Nest Thermostat to automatically shut down heating system to prevent it from making it worse. Google Nest Thermostat - The 3rd generation Google Nest Learning Thermostat is slimmer, sleeker and even more beautiful. With a bigger, sharper display and Far sight, you can see the time or the temperature you've set from across the room. And now it even controls your hot water tank. The Google Nest Thermostat learns the temperature you like, then programs itself. It uses built-in sensors to confirm no one's home and It knows how long it takes to heat your home so you're comfortable when you get there. When you leave, it turns itself down so you save energy. And you can check your Energy History with the Google Nest App to see how much you've saved. Google Nest Protect - Know more, worry less. The new Google Nest Protect looks for fast burning fires, slow, smoldering fires and invisible carbon monoxide. It speaks up to tell you what the problem is and where it is. It can also give you a friendly Heads-Up before it has to sound the alarm and you can hush it with your phone. In case youre not home, Google Nest Protect alerts your phone when the alarm goes off or the batteries run low. It also gives you peace of mind by testing itself over 400 times a day and showing you everythings working with a quick green glow when you turn off the lights. And it looks after your family for up to 10 years.