PID controller on Arduino base. We use it to control the mash temperature.
Most of this code is based on the work of Bill Earl for the Adafruit Sous-vide tutorial using an Arduino. Check it out at http://learn.adafruit.com/sous-vide-powered-by-arduino-the-sous-viduino.
Our modifications are a cheaper Display shied - such as the DFRobot Arduino keypad shield.