Arduino Uno sketch using the standard Wiznet Ethernet interface. You can access the setup page from "Default IP"/setup, at which point you are able to setup networking info as well as what Companion button you would like to trigger over OSC. By default it is monitoring Pin 2 to be pulled HIGH, and a rather long debounce time, which is all adjustable.
sydneyjd/Companion-Arduino-Uno-OSC-Controller
Triggers setup specified Companion button on button press
C++