I'm actually doing kinda the same thing with an arduino, SSR's and 1 wire temp sensors. I tether the arduino to my laptop for control and logging though.
You should look at brewtroller.com. It's basically running on a modified arduino on a specially made board. They done some pretty cool things like use pressure sensors to measure volume on the vessel. I'm working on adding it to my system.
steve- that all sounds awesome, but way over my head! I'm hardcore into DIY stuff (check out my basement brewery thread) and somewhat into computers, but not that hardcore! I'm just a run of the mill grease monkey here!