Following the example in the Sympathy Remote thread, I was able to connect my Logitech Companion to my Raspberry Pi. Button presses on the Companion show up at key presses in the system. Almost every button shows up as unique using the python Keyboard module. The exceptions are the Off, Music, TV, Video, Red, Green, Yellow, and Blue. Most of these work without much modification to the json files. This is interesting because I would rather use the the Harmony Companion as it is what the family is used to and the feel is generally nicer then the low-cost remotes I've gotten from Amazon and Aliexpress.