La Crosse Alerts Mobile 926-25000-WGB Wireless Monitor Add-On Sensor Only for existing La Crosse Alerts Mobile System Remotely monitors sensors 24/7 using a APP. Perfect for...Backyard temperature and humidity; Plants, gardens and greenhouses; Refrigerators, freezers; Food storage; Sensitive electronics; Outdoor pets and livestock; and so much more Temperature and humidity measures: (1) Ambient air temperature; (2) Ambient humidity Temperature range: -40 Degree F to 140 Degree F Requires 2 AAA Alkaline batteries (not included) Text and E-mail Alerts first 3 months FREE; 1 year subscription available after for $11.88 yearly ($0.99 per month)