I thought I'd start a thread instead of posting in another and have this buried. The iSpindel is a fairly young project and is developing all the time. It is fairly simple to build and the instructions are here: http://github.com/universam1/iSpindel/ I recommend using Google translate when following the build pictures as it is more complete than the English documentation. It had cost me under $50 to build. It is monitored on the internet via ubidots.com and the developer of brewpiless (brewpi via a single wifi board) is integrating it into his project so you can have fermentation profiles that follow s.g. rather than time. The materials are all available cheaply on ebay. There is one issue that is not fully resolved on the github page. Instead of a 470 ohm resistor, use a BAT-43 shottky diode. The iSpindel has a deep sleep mode and with the resistor it sometimes goes into deep sleep. The drawer or sled which slides into the bottle is 3D printed and the design on Github does not easily fit the xxl pet bottle blanks available on ebay. This design does fit: https://www.tinkercad.com/things/1TcD78DvxQu It also has a spot for a 20g calibration weight from ebay ($1.54). This is to help the hydrometer tilt at an appropriate angle. Mine is a work in progress. Will keep you all posted.