WxImp Agent and Device Code
WxImp is an Internet-of-Things enabled weather station that can be built for less than $35 if you have access to a 3D printer. Check out the progress of the project on the WxImp page (https://https://richard.milewski.org/blog/wximp/). All of the code is released under a Mozilla Public License and the .stl files to print the mechanical parts yourself on nearly any 3d printer are released under a Creative Commons license.