While looking for liquid level sensors online, I came across this guy from Sparkfun: http://www.sparkfun.com/products/9072

It's a potentiometer strip which would attach to the outside of the keg, and can sense the liquid level without having to go inside it. The only hurdle I see is that it requires a magnet on the inside to be able to detect the liquid level. Does anyone have any thoughts as to how you could get a magnet in there that would float with the liquid level, instead of just clinging to the metal on the inside of the keg, but would also not produce off flavors in the beer? I'm thinking maybe attaching it to the dip tube in some fashion, but I'm not sure.

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If you are using this on an aluminum corny keg I imagine it would work no problem. You just need to figure out how to get the magnet to float. Perhaps some kind of foam float that mounts around the dip tube, that way it is next to the outer wall of the keg and the sensor can be lined up accordingly.

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Hey, that sounds great! For some reason, I spaced on the thought that the corny kegs are made of aluminum. Now to figure out a float. I'm thinking a piece of Styrofoam, like from a cup would work pretty good.

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The only challenge I see is getting the magnet to read on the outside of the keg. You will def want a powerful magnet, I'm thinking rare earth, this would ensure it is light enough so you don't need a foam brick to keep it from sinking.

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The only concern I see with a Rare Earth magnet would be it imparting off flavors into the beer.

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