La Crosse Technology TX141TH-BV2 Wireless Outdoor Thermo-Hygrometer Transmitting Sensor

Wireless transmitting sensor sends accurate & fast outdoor temperature and humidity measurements with its 433MHz frequency. Place sensor in a dry, shaded location to protect from moisture build-up and direct sun exposure (may cause higher readings.) A proper location is on the North side of your house, about 18 inches under the eaves. Weather resistant case and battery powered.