Cambell dataloggers would lend themselves well to this application. Most have several control ports cabale of going high/low in response to an input from a sensor. And thus would be capable of tripping relays to control devices. They are easy to monitor from a computer. Infact, you can even connect them to a cell phone or satalite modem and work with them from anywhere.
The programing is hassel at first, but once you get the hang of it it is pretty easy.
You can buy pre-made temprature sensors from Cambell, or do what most do a get stuff from Omega and build your own thermocouples (super easy). Pretty much any device you can pull an analoge signal (strait up voltage) off of you can read with a datalogger.
If anybody goes this route and would like some help shoot me a line. If I don't know the answer, I work with some people who know this stuff inside and out who will.