Wireless, battery-powered, DS18B20-based sensor nodes that are IP65 rated.
Full write-up here:
http://www.cupidcontrols.com/2014/08/adventures-in-moteino-remote-temperature-monitor/
If you really don't like reading, scroll down to the bottom and watch the video, or catch it here:
https://www.youtube.com/watch?v=Dh7epndyqPw&feature=youtu.be
Cheers,
Colin