This will explain the why of things. To see just the final product look at the build instructions.
This was an obvious choice since I had it lying around and am mostly familliar with it's USB functionality (or at least I thought so before I started this project). It is small in size and has a few IO pins in case I need to add more functionality in the future.
Used it in case I need to add more buttons in the future and because I had some partly broken ethernet cable lying around. Could be replaced with any 2 wire cable.
No rationale just a generic push button.