The hardware is designed to be modular and extendable. The Base contains everything to make the ESP8266-01 run and connect to the other modules. This includes several (optional) power connectors as well as Buttons for programming and restarting of the Chip. In addition there are the pinholes for connecting to the other modules.
Please download the following two repositories:
The first repository contains the schematics, gerber files, ... to actually order and build the hardware. The second repository contains the firmware for the ESP8266 to communicate with the App.