A few months ago I had 2 great brews on tap. Naturally, one of them blew dry while I was entertaining guests - “Sorry guys, it’s just the porter now”. Straight afterwards what do you know? The porter blew dry as well. This happens to me a lot and it seems like kegs always abide by Murphy's law. Generally I have a ballpark idea about how much is remaining in my kegs, but I hate lifting or shifting them when they get low because it rouses the slurry and my next few beers pour cloudy. Surely there’s a solution for this problem right? I scoured the internet, credit card in hand and it turns out... there are several options: -If the weather’s right you can warm your kegs and watch where the condensation forms, but this is difficult if you can’t reach some of your kegs (think the third keg at the back of a kegerator, or vertical kegs stacked like sardines in a keezer setup). In my experience the condensation takes a long time to form and I find it tedious. -There’s a cool product called Ball and Keg that uses floating magnets to give an indication, but it’s equally restrained if you don’t have easy visual access to your kegs. -Then there are these awesome DIY open source projects like KegBerry and Raspberry Pints, but I find them to be overcomplicated with loads of wiring and after you cobble together all the parts, you’re looking at a serious investment in time and money. (There are many more options out there with similar drawbacks that I’ll omit for brevity) I totally would have bought into one of the existing solutions but none of them really spoke to me, so for the past few months I’ve been working on yet another keg monitoring system. The idea is that if you take a digital bathroom scale then add bluetooth, you now have the basis for a no-wires keg monitoring system that can talk to almost any modern mobile device. Some of the open source guys have tried using scales in the past but couldn’t get it to work, hence splicing flow sensors into their beer lines instead. I gave it a go anyway, logged measurements for days and found the results to be very linear in proportion to temperature so it’s actually quite easy to get an accurate measurement. Here's a pic of how the weight reading varied along with changes in temperature. This was just weighing a keg full of water for a few days. Using that correlation we can compensate for the temperature to get a much more stable measurement of the keg's weight, however, it may not even be necessary. Here's that same data when you chart it with the zero point included in the plot. As you can see it's pretty darn flat and that's with temperature variances of about 6 degrees C. If your fridge has temperature swings of 6C it's probably on the frink Here's are some pics of one of my first test setup. I used a cheapo bathroom scale and hooked it up to a Spark Core to upload measurements to an online database. And here’s the super ugly prototype I’ve been working with most recently. I got the glass cut at a local glass shop, but it's pretty dodgy and not very round. Meanwhile I've been buying and tearing apart all manner of bathroom scales to see how they're built and learn from their designs. The awesome thing about the bluetooth scale approach is that you don’t have any wires and you don’t have to splice anything into your beer lines. Bluetooth 4.0 (or BLE) uses very little power and it looks like we’ll be able to get a couple of years of operation from a pair of AAA batteries. I taught myself iOS (swift) and began writing a demo app to interface with my bluetooth sensor and it quickly became evident that adding a fully featured tap list would make a lot of sense. That way you can leave your tablet with your kegerator when you have guests over and it behaves like the chalk board at a tap house - a digital tap list showing what’s on each tap, vital stats and telling a story about each beer, and of course showing how much is remaining. Following are some screenshots of the app as it's was being being developed. At the moment there are no scales in range so the fill levels aren't being displayed, but you get the gist... And here's an early version running on my iPhone. I gave the app a trial run a few weeks ago at my son’s first birthday party and it was surprisingly popular with our family and friends! I got loads of questions about my beers and I noticed a lot of guests were treating it like a wine tasting event since they had the app telling them what’s on each tap and describing the styles and flavours of each of the beers. Anyhow, we haven’t settled on a name yet, but one of my favourites is Barmaiden - as a nod to the way it keeps inventory of your kegs and also tells your guests about your beers to help them choose between them. Now it’s full steam ahead with the software and I'm also working on the 3D models for the scale part, but I really wanted to post this here on AHB sooner rather than later because I know you guys are going to have loads of awesome advice in these early stages of the design! Ideas? Suggestions?