ok there has been alot of good points.
tanga, I built this for myself and im sharing it with you all, if someone wants to make it a sell it good luck to them, I'm a big believer in karma and also there is nothing to patent.
Arniew your right about the arduino shell, it would work out well as there wouldn't be many parts and ppl can change the program as they like, I have just started to play with arduino's at work to do basic circuit breaker controls and testing.
Zizzle, you are completely right .
If Im going to do this it would be a single board design to reduce the number of connectors because they are pricey, I would supply the board, the parts to go on the board, a programmed chip, lcd screen and a DS18B20 temp sensor. the things that need to be done would be,soldering parts to the board, the box, a 12V power supply, a SSR and the 240v wiring. the wiring would be akin to wiring a stc - 1000 and a PID combined. I still haven't made up my mind if im going to do this, it will take a bit of time to design the board and get it made and order all the parts, I did a quick addition today and it would cost about $50 - 60 plus delivery, I need to work out the design before i could get a more accurate price.
my controller differs from a PID controller in that it controls the heating element and the pump, has a manual and auto mode, a user friendly display with prompts like 'add water' 'remove grain'
up to 5 programmable steps, 5 programmable hop addition alarms and it still has a PID algorithm controlling the heating element.
cheers matho