I did some quick tests and everything looks good but I don't really have an Arduino project set up right now to test with properly. I will try to get to this but hopefully someone else will try it too.
This plugin might also be useful for those with audio receivers that accept control by serial. In that case it might be necessary to send more than just regular strings. Sometimes they need hex codes that ASCII does not cover. I handled this in the TCP plugin by parsing strings that look like \x0A in to a byte with decimal value of 10.
Anyway, I'm happy to see people working on plugins for VoxCommando!