With a little help form an Arduino you can do it. Read the temperature with the arduino and send it to the Pi over USB. Open the USB port with a simple C program and read what arduino is sending. After that is up to you if you want to trigger valves, apply power to a relay to tart a motor etc. It is very simple.
I was thinking about this PT1000 temperature sensor since I want to measure the temperature on the solar collectors and the 1-wire sensors are not that good for temperatures above 80 degrees. Is there any digital alternative to 1-wire that could be easily used with pi without interacting over third party devices like arduino?