Today I tested if it ws possible to use the small esp8266-01 together with two i2c boards to make a gamepad. It worked pretty well, except that I need to figure out why the response is slow. Probably due to the rest API, but it could also be some waiting for the A/D conversion.
The Esp8266-01 contains a small webserver so that it's possible to connect to it using the browser to see what i2c devices are conneted on the bus. The joysticks are simply potentiometers so I connected them to the four A/D channels on the Ads1115 A/D converter board. They also contain switches, so they are connected to the pcf8574 i/o expander board.
Links to the different services used:
The box is available here: http://www.thingiverse.com/thing:2134841
The script I'm using is available here:
I also made a small video where I explain more.