I bought my Interactive Network control unit in November 1992 and I was an IN addict until the company went under in June 1995. During that period I won about $15,000 in prizes including a massage chair, TV, stereo and a computer.
Interactive Network was initially only available in northern California with expansion later to the Chicago area.
Playing along with Jeopardy! at home with multiple choice was a fun experience. Players were also allowed to choose two categories per round to have the clue values doubled, so scores in the 300,000s were possible.
Every so often the company would have live tournaments. Home players with the highest scores over the qualifying period would gather at a hotel and compete in person. Each person brought their control unit and played along with three Jeopardy!games (ones previously aired a few years back at the time) shown on a TV. Best scores from two out of three determined winners.
(On the same day was also a live tournament for Wheel of Fortune.)
I was not the only IN member to later make it on J! for real. This guy: http://www.j-archive.com/showplayer.php?player_id=3046 also made it on the show, but he ended up with a tough draw unfortunately.
Here is a photo of the control unit:
