Nest just announced a new $39 Temperature Sensor that works in tandem with the company’s smart thermostats to keep particular rooms in your home at the ideal temperature. The device is scheduled to ship in April, and there’s also a $99 three-pack available for preorder. To use it, you’ll need the latest-generation Nest Learning Thermostat or the Nest Thermostat E; the Temperature Sensor doesn’t work with first-gen or second-gen Nest thermostats.

Setting up the Temperature Sensor is pretty simple. You put it on a wall or shelf, add it to your Nest system in the Nest app, and choose the temperature you want for the room it’s in. If you’ve got multiple sensors around the house, you can tell Nest which one to prioritize at a certain time of day. Each sensor can be placed a maximum of 50 feet away from the Nest thermostat it’s linked with. If you’re curious, Nest says you can pair up to six Temperature Sensors with each Nest Thermostat. That grouping can be repeated up to three times for a maximum of 18 sensors.

I wish I had a house big enough to warrant 18 temperature sensors. Don’t you? Doesn’t everyone?

Nest’s Temperature Sensor isn’t quite as advanced as some competitors. Rival Ecobee makes one that can detect when people are actually in the room and automatically gives priority to occupied rooms. Ecobee’s sensors can also be programmed to always be active, so it can balance the system for hotter or colder parts of your home. Plus, Ecobee bundles a temp sensor in the box with its thermostat. Nest isn’t going that far, but it is offering a discount when you purchase the temperature sensor with the Nest Thermostat ($20 off) or Thermostat E ($10 off).

Whichever you prefer, both approaches acknowledge that the temperature reading from your main thermostat — however “smart” it might be — won’t always be true throughout the house. Maybe it takes longer for your bedroom to warm up than the living room where the main Nest is. This product solves that. These sensors make the whole system more accurate and keep things comfortable. That might come at the cost of overheating another area of your home that you’re not in, though. Unless you’ve got smart vents, heating systems are nowhere near precise enough to set different climates for each room.

Apart from the Temperature Sensor, Nest has also officially launched its Nest Hello video doorbell for $229, and the long-in-the-works Nest x Yale door lock is finally, really, actually shipping for either $249 or $279 (with included Nest Connect). The video doorbell requires a wired connection with power, which makes it a non-starter for me since I prefer units that at least give you the option of using batteries. But if you’ve got the setup for it and are in Nest’s product ecosystem, it could be pretty compelling!

These set of releases further pits Nest — now once again under Google — directly against Amazon’s Ring and other companies in the battle for smart home dominance, whether it’s doorbells, cameras, or even just a sensor.