This is work in progress and specifications are not completed yet.
The latest completed prototype schematics and PCB designs are available on 123d.circuits.io at this address: http://123d.circuits.io/circuits/58269. Boards could be ordered from oshpark.com at this address: http://oshpark.com/shared_projects/bFNU3LQB.
The current work in progress is located on 123d.circuits.io at this address: http://123d.circuits.io/circuits/66662.
At the moment you could use this post as reference.