FYI, for today only (while supplies last), Woot's 'sellout' site has a wireless thermometer that some folks may find useful @ $9.99 + $5 shipping. You can order up to three of them and shipping remains $5, so ... for 2 you're looking at $24.98 shipped, and 3 will set you back $34.97.
The remote wireless temp sensor can transmit up to 100' with no obstacles, so it could be ideal to keep he base station in the house and the remote temp sensor in, for example, your greenhouse or near your plants outside to monitor temps around the pots for heat/freeze. Runs on batteries but also has solar cells to extend battery life. The outdoor sensor is good from -4 degrees Fahrenheit to 140 degrees Fahrenheit (-20 degrees Celsius to 60 degrees Celsius).
I've done plenty of business at Woot (50+ purchases over the years), solid company to do business with. Easy to get addicted to checking their other sites (woot.com and deals.woot.com) every day.
Anyways ... I'm buying two to add to my current thermometer setup, thought I'd share.