Rattus_Metallum made a cool DIY MIDI foot controller.
He needed something to control scripted chord progressions in Dreamfoot, an app for free-floating synth pad accompaniment and was inspired by the iRig BlueBoard, but wanted to dumb it down a bit. He made use of a Teensy 3.2 microcontroller to interpret the switches and send MIDI data over USB. The code for the Teensy was posted by Liam Lacey at Ask.Aduio.