@bx a) So I do open source all my projects so that'll be board + schematic (including bom) + code + 3D cad files for box and the actual pen thing. I probably won't publish instructions though - both because I don't enjoy writing instructions and because I'm a teeny bit wary of people using this device; I believe it to be pretty safe but it is obviously not certified in any capacity and could totally have problems that I've overlooked. I would be very sad if anyone got hurt
b) basically the resistance between your body and the can goes down the harder you squeeze. I'm not sure on the exact mechanism but it is pretty non-critical on the conductor