GBZ Main Board
A Raspberry Pi Zero is the recommended starting point.
A Raspberry Pi 2 or 3 are usable, but will require manually removing the USB ports, ethernet ports, GPIO headers, and possibly ripping the PCB down in size.
The new Raspberry Pi Zero W will also work, making WiFi and Bluetooth dongles non-necessary.
Not Tested - Advanced
These systems are available and roughly the same size as a typical Raspberry Pi, and have been used or theorized to be usable by some of the more advanced modders.
| Intel Core M vPro STK2MV64CC stick
| UDOO NEO