The foot pad is really one of the biggest innovations for the project. The current version really isn't much different at it's core than the prototype, but there are some major improvements.

First, the FSR elements are fully integrated into the PCB. A typical FSR is just a layer of conductive rubber over top of a bunch of interlaced fingers. When you put pressure on the conductive rubber, it contacts the interlaced fingers underneath. The harder you press, the less resistive the connection becomes. To save money on a custom pad, I put the pattern I wanted directly onto my PCB (I used an Eagle script!), and just had to put one large piece of conductive rubber over top.

Here's a video of the 2nd Gen foot controller. It's wired, but has an integrated MCU and communicates with the control PCB over UART:

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Here's the latest, Gen3 Foot Controller PCB. You can see the interlace pattern and the six "string" zones. The area between and around the string zones are linked together to form one big auxiliary FSR zone. This way, even if you aren't ready to strum the strings, the user can essentially set the dynamic level in advance. It's a feature that's not tested yet so I won't talk about it any more, but the electronics are there for when I'm ready to implement dynamics.

The 3rd Gen foot controller is wireless (NRF chip on the far right), and has a rechargeable lithium-polymer battery that will last 12-14 hours. It also had indicator LEDs for charge state, low battery, and control activity. The main MCU is an ATmega, which is to the left of the Nordic RF chip.

Here's the 3D model of the full assembly. The pad area actually would have the padding layer and outer contact paper layer on top, but those aren't modeled. I have a prototype, but I'm traveling at the moment and can't take a picture...