CoCoIO is for those who want to experiment with ethernet on the CoCo. We are not relying on another computer like RaspPi or ELF32, there is no serial terminal involved. The user manual (online here) links to a little DECB and some OS9 utilties (arp, dig, ping, dhcp, and the like). But mainly, check out 'frobio' - Henry Strickland has given us the code for the included boot ROM, the server that feeds it, and a whackton of 'waiters' to serve operating systems and more.
Compatibility - almost all CoCo2 and all CoCo3 are 100% compatible. CoCo 1 C,D, and E boards must be used in a mutlipak. We'll fix it and change our tune, once we figure out why. As always, CoNect offers 30 day returns, if it doesn't work on your CoCo just email for a return label.
Wifi - CoCoIO is for wired ethernet, however a wifi extender like the TPLink re105 ($15) fills the gap with a wired jack on the bottom. You will need a modern computer to configure it, after that it 'just works' with CoCo.