What is arduino you ask? Well, I've been hearing this word connected to cool projects for a while now and come to find out, it's a small computer board that can be programmed to help computers sense the physical world around them. This can come in the form of a robot (like the Mars rover), a weather station, or hundres of other cool applications.
BrewPi uses arduino magic as an open source fermentation controller. It can control your beer temperature with 0.1 degree precision, log temperature data in nice graphs and is fully configurable from a web interface. Read about it here.