Review on 🌡️ 5-Pack Mini Digital Thermometer Hygrometer for Indoor Rooms - Monitor Temperature & Humidity, Large LCD Display in Fahrenheit or Celsius - Ideal for Greenhouse, Home, Reptiles, Humidors, Office, and Garden by Daniel Truett

These are great, not only do they come with batteries but they also come with an extra set of spare batteries and 3M tape. I hang them all over the house and also have one on my wife's bedside table. If she goes to bed and says she's cold, I can use that to gauge whether I need to turn on the heat or just give her a hug! Note that the sensor opening is on the back. So if you want to use them in a room, you have to leave some space behind them that is also open to the room.