The guys over at Initial State have written a comprehensive tutorial to create an Internet of Things Beer Fridge! By using a Raspberry Pi, some sensors and a Wii balance board (!), the software is able to determine how many beers are in the fridge, whether the door is open or closed and the temperature inside the fridge. The output is streamed to their online data service which you can then look at using a tablet/phone/browser. Read more here.