I thought everyone working on this thing gave up, but it looks like a functional revival for XBAND has entered an open beta of sorts. XBAND was an old cartridge modem used for playing Genesis and SNES games online, sending mail to other users, and more. It was officially licensed by both Nintendo and Sega.
You can connect with a landline, a modified dreampi, or a voip setup similar to what's used for Saturn. Unfortunately gameplay is going to be really laggy due to the nature of this sort of technology (and doesn't even work at all using dreampi), and it's unlikely that any further improvements will be possible, but it's still cool.