This is the wireless temperature alarm that I use...the air temp/humidity monitor #6278...
http://www.waterwarehouse.com/poolsu...LAID=318968249
I orginially bought mine from RadioShack, but I don't see them offering it anymore. The #6278 Air Temp/Humidity monitor has a range of 300 feet. I've had mine for about ten years and it still works flawlessly. My greenhouse is 250 feet from the house and I keep the receiver next to my bedside. It has a Minimum/Maximum memory file and Min/Max alarms that you can set for both the air temp and humidity. Transmitter is weatherproof. Both the transmitter and receiver use 2 AA batteries which last well over one year. Hard to beat all that for under $90.