So, I had a chance to review this further. First off, I must say that this unit is packaged very nicely, and is quite easy to set up. The unit comes in two parts, the "sensor" which is basically a plastic ring with a cord. The cord has a weatherproof 4 conductor 3.5 mm connector that connects into the "hub." The unit comes with 4 Energizer batteries and a small screwdriver to add the batteries. You download an app from either Google Play store or the iTunes store, depending on your mobile device. Once downloaded, you start the app and install a new device into the Wink app. This can be done by selecting the Quirky Refuel, or by scanning the barcode on the box (very slick!). The app then takes you through the process of connecting to your local WiFi. From the app, you select which WiFi network you want to join (the hub detects this), and then you start the link up between the mobile device and the hub. This involves putting your mobile device on the top of the hub, where they link up via a series of screen flashes. Once they connect, an LED on the face of the hub lights up green. A series of 5 leds on the top/side of the unit light up to show the tank level. This is also displayed in the app (e.g. 3/4 full, tank empty, etc). This is a very high quality unit, and I am amazed they sell this for $30. Someone must be losing some $$$.
As for measuring beer levels... this might take some doing. I am pretty certain that the sensor uses strain gauges, esp. given the 4 conductor connectors between the sensor and hub. Also, pressing down on the sensor reveals smooth transitions between the different LED states. The problem is that a standard corny keg is a bit too wide (as is a 1/6 barrel commercial keg). The corny sits nicely in the sensor, but the rubber base on the corny prevents contact with the surface of the sensor that does the measurement. Even so, it might be possible to modify to work without much trouble. The sensor itself is only slightly wider than a ball lock corny keg, so it might be possible to fit two of these into a standard kegerator. Incidentally, the app does allow you to specify a tare weight for an empty tank, so it might be possible to use this unit for beer measurement after all.
BTW, I looked inside the hub and it contains a single round circuit board with what appear to be some small surface mount components (e.g. resistors, capacitors, small ICs), and an Electric Imp 2 daughter card. The EI2 daughtercard is soldered directly onto the round circuit board. I don't know much about the EI2 but, it appears to be an SoC with an integrated WiFi chip. Pretty slick! More info here:
http://electricimp.com/product/
I'm not sure about the OS but it may be possible to hack this to render output more appropriate for the task at hand. In any event, I think this will certainly be useful to keep track of my propane!