The WeMos D1 Mini is a fantastic little development board based on the ESP8266 microcontroller with WiFi. It’s super cheap, and there’s even support for it now in the Arduino IDE so you can program it easily. If you haven’t seen it before, check it out on the WeMos site.
One limitation is that it needs 5V USB power to run, which is a pain if you want to build it into a project that doesn’t have USB power easily available. I designed this shield to give the D1 Mini the ability to accept power from 7 to 14Vdc (up to 20Vdc in a pinch) via a 2.1mm DC jack or screw terminals.
I hope to turn this into a product soon: I just need some more parts to arrive. There’s a page for it now at www.superhouse.tv/d1mpower.