Discussion of the XBAND Video Game Modem and Network.
XBAND was an online gaming system for consoles, first sold in 1994. Hardware was developed for the Sega Genesis and Super Nintendo Entertainment System (SNES) that allowed supported games to be played over a phone line. An online service provided game matching and e-mail. The system was later expanded to include the Sega Saturn.
A description of the product and service can be found on wikipedia.