That device is most probably a DS18B20 in a weather proof package. They are available in a simpler flat-face package that would be more appropriate for your needs for about half the price. The maximum temperature for them is 120C. The performance might be a bit of an overkill for you but they are so good and easy to use, so well-suppoorted, and so cheap that you need some pretty persuasive reasons to use anything else.
Here is some background