<$7 WiFi Firmata microcontroller, with arduino pro-mini + ESP8266, or...?

Hey, I've been messing with johnny-five, a framework in Node.js that supports devices using Firmata, especially arduino.

I can do serious logging and processing on my server running johnny-five, and use a Firmata-enabled device to simply actuate motors/lights/etc and feed sensor data into johnny-five. It's easy to get this working over USB, and apparently it's easy and inexpensive to get it working over radio or bluetooth (the parts are slowly making their way from China to my house as I type!).

But, I want to use Firmata over wifi. Then, anywhere there is wifi, I can connect to my johnny-five server and relay information.

Also on the slow boat from China is my ESP8266. I haven't worked with it, just read about it. Is there any way to put Firmata on it, or to set it up with NodeMCU or the new Arduino IDE suppoer for ESP8266 or something else so that it will act as a transparent wifi layer between my remote server and an Arduino running Firmata?

Alternatively, has anyone put Firmata on an ESP8266? Is it possible?

Lastly, is there any other cheap, WiFi-enabled, Firmata-supporting microcontroller that would let me do this?

Thank you!