We use the term 'DIY' loosely. The only way we could do this ourselves is with a stack of textbooks nearby. The whole project is a cluster of force-sense resistors, tekscan circuits, an Arduino mega and XBee wireless communications (extra points for you if you know what all of those things are, because I sure don't). But the result is a kegerator monitor that we'd love to see hit the shelves.
An LCD screen on top of the kegerator prominently displays the amount of beer left in the keg (calculated by weight), the temperature of the beer and the CO2 levels. The same info can be shown on a computer screen over a wireless connection.
How long before we can keep up with our kegs via mobile phone or on Twitter? If a London bakery can tweet when there's hot rolls fresh from the oven (Yes, it's real, and it's called BakerTweet), then our favorite neighborhood bars should tweet when they tap a new cold keg!