This is yet another USB footswitch / macro keyboard and I use this as a foot controller for my teleprompter.

The design is based on the Arduino Pro Micro, which features USB HID functionality.

The software can be found here:
https://github.com/tkilla64/footswitch-usb

The following hardware is needed:

6 pcs of M3x6 (DIN 912) Hex socket cap head screws
4 pcs of ST2.2x6.5 self-tapping screws
4 pcs of compression springs 0.7x9x15mm
4 pcs of Cherry MX switches
40x60mm prototype PCB
Arduino Pro Micro