How much on tap?

1.) A Beer by the Sensor
http://bits.blogs.nytimes.com/2013/11/08/a-beer-by-the-sensor/?ref=technology2.) Category: Technology
3.) Level: National
4.) Content: A means to measure the amount of beer left in a keg
5.) Importance: Honestly... not much other than to help bars/restaurants run more efficiently.
6.) I just thought this was kind of a cool concept that I can't believe nobody has thought of before. For anyone that has ever worked as a bartender, whether it be in an actual bar or in a restaurant, you know how incredibly annoying it is when a keg runs dry. First of all, it always seems to happen when the glass is almost full, and then you get that burst of foamy air that splatters beer all over you. Don't get pulled over on the way home, because most police don't buy the excuse that you smell like beer because it spilled all over you. Second, the keg never runs out when that is the only thing you have to do at the moment. Oh no, it usually happens when you have 20 different drink orders at your bar top, tickets rolling out of the printer faster than you can read them, and some drunk guy that never went to college is trying to tell you about how "his" college football team is going to beat some other crappy team you've never heard of next year because they have a new quarterback coming in from nowhereville Tennessee. Anyways, in moments like that, it sure would be nice to have some means to tell that the keg is running low. It won't shutup the drunk guy, but atleast it could cut out one of many stressors of the food service industry.