Your beer is dangerously low

I have been known to enjoy a cold beverage on occasion. The odd snifter of port at Christmas or a cleansing ale after completing a marathon always goes down rather well. One problem I have noticed is that I often forget when my beer is empty, I just keep drinking without realising that in fact all I was sucking in was cold cold air without any beer goodness at all. Well know this fancy talking beer glass solves all my problems. It warns me when my drink is running out and prompts me to get another beer and refill it. Pure genius.