Some sensors collect data, transmit it to a radio, which is picked up by a reciever machine, which writes it into some storage for display.
The sensors are called "Digoo DG-R8H R8H 433MHz Wireless Digital Hygrometer Thermometer Weather Station Outdoor Sensor for TH11300 TH8380 TH1981".
For these, I paid $3.82/item delivered in 2019. The price appears to have doubled in 2022.