I bought this Sharper Image Thermometer to monitor the temperature in my greenhouse from inside the house. Now I don't have to worry about the temperature going too low and not knowing it. This Thermometer is wireless and can be set to read in F or C. The base unit shows the room temperature and the temperature for up to 3 remote sensors. The unit comes with one sensor, but others can be purchased separately. The sensors will transmit up to 328' from the base. There is a 12-hour chart that shows the temperature trends, and when you press the memory button it will show the high and low readings in the last 12 hours.
One of the features I like the most is the Freeze alert, which sounds when the temperature hits 37.4 degrees. This has saved my plants from being frozen a couple of times, when I have forgotten and turned the heater off. The base takes 2 AA batteries and the sensors take 2 AAA.
I have had this Thermometer for about four or five years now, and it has been trouble free.