I'm a homebrewer too, and plan on a project like this soon. Rather than arduino-ify the fermentation portion of the process, I am leaning more towards the mash. American science surplus has these cool little heaters from coffee pots right now and they are dirt cheap (2 for $1.25) I got 4 or them and plan on pump the mash liquor around them (in copper tubing of course) to give me a fully programmable and consistent step up and possibly even programmable decotion mashing. How about an update? How's it working for you?
The heaters I was talking about http://www.sciplus.com/recommend.cfm/recommendid/4157
My plan is to use this relay Solid State Relay - 8A - COM-10636 - SparkFun Electronics with a pot to adjust pwm in to the relay. I'll be using one of these Thermistor 10K - SEN-00250 - SparkFun Electronics to monitor temperature and would very much like to add my http://www.sparkfun.com/products/10168 to the project for visual feedback since it's doing little more than occupying space in my parts box right now. But, as of now this project is beyond my capability.
It does seem easy enough, I just have to learn , ie get these guys to help me, to do it.
What a great site, I love this place! Who needs school when you got all these brilliantly deviant minds in one spot on teh interwebz?