Oh god.. there were 2 or 3 Genesis modems if I remember right. One that was released soon after the genesis which would allow you to dial up a friends house and play.. but it never got supported and probably died before it made it off the production floor.
There was a modem -TYPE- device that you could hook to the Genesis and download games and demos thru the Sega Channel if you had cable. That never came to my area, and I live in the country so I never even had cable until the whole minidish craze got started.
The Xband was a 3rd party device I think.. and they made one for both the Genesis and the SNES. I\'ve seen them at McVans videogame trader but never felt inspired to pick one up since barely anyone in my calling area has a genesis still, let alone the modem for it. I wouldn\'t even know what games were compatable with it. And no, luckee, it was for the Sega Genesis.. although they might have also made SegaCD and Sega32X games for it as well.
The later models of the Saturn had a modem included, and also a keyboard if I\'m not mistaken. Even though DC will probably be seen as the main forerunner of Online consoles, Saturn was actually the first Internet capable/ready console.
You might talk to the resident Sega freak here, DJRazzyFantastic, or AlteredBeast as most people know him. If anyone on these boards would have one, it\'s him.