@ianf: a great suggestion. I have actually been experimenting with ESP8266 quite a bit a little while back and I’ve developed the ESPToy:
http://rayshobby.net/cart/esptoy
The pricing, Arduino IDE support, community support, and hardware capability all make it a very attractive platform. There is no immediately plan to change OpenSprinkler to use it yet, mainly because even though it looks like a better platform, it takes time to iron out all engineering issues. Instead, we are working on a different product that uses ESP8266, which will pave the way for OpenSprinkler to eventually use ESP8266. In any case, if you build an OpenSprinkler based on ESP8266, be sure to share it. I am sure many people are interested. Thanks.