MyoWare Muscle Sensor Kit
The MyoWare Proto Shield passes all signals to a bit of protoboard. Use this area to solder on whatever custom circuitry you can come up with.
The Cable Shield and the Proto Shield have two rows of 3-pin plated through holes on each end. 'Standard' 0.1" headers to be used to stack them with other boards. Using a combination of male and female headers, this can reduce the profile of the stacked boards.