An anonymous reader writes: Google's recent acquisition of Nest, the maker of smart thermostats and smoke detectors, has sparked concerns of future plans for the devices, and how Google's omnipresent thirst for information will affect them. Thus, a team of engineers at Spark sat down and roughed out a prototype for an open source version of Nest. It looks surprisingly good for such a short development cycle, and they've posted their code on Github. The article has a number of short videos illustrating the technology they used, and how they used it. Quoting: 'All in, we spent about $70 on components to put this together (including $39 for the Spark Core); the wood and acrylic were free. We started working at 10am and finished at 3am, with 3.5 engineers involved (one went to bed early), and the only work we did in advance was order the electronic components. We’re not saying that you can build a $3.2 billion company in a day. But we are saying that you can build a $3.2 billion company, and it’s easier now than it’s ever been before.