Jack LaLanne's Physical Conditioning for Intellivision
Ian Bogost, guest editing at Kotaku, shows off his copy of "Jack LaLanne's Physical Conditioning," a tape-based game for the Intellivision. Published in 1979, he guesses that it may be the very first "health" videogame.
No screenshots, but I imagine the first challenge simply prints on the screen: "Tow boat across nearest harbor using only your teeth."

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If it's a cassette, then this would be for the Mattel Aquarius add-on for the Intellivision.
Because, I find it hard to believe that my complete collection of Intellivision-related gear would be missing a cassette interface and I'm pretty sure there was never an Arcadia Supercharger made for the Intellivision. :)
It's not a videogame, per se, but it may be preceded by an 8-track cartridge for the 2-XL, which is one of my favorite childhood toys. I don't think I had the one in question, and I doubt there was much more than a simple few exercises, but it had to have possessed some pseudo-interactivity, which puts it in the right ballpark.