If you really want to keep it Twitter-specific, the person who joins the call could also auth via Twitter and I think you could verify that they actually follow

If you really want to keep it Twitter-specific, the person who joins the call could also auth via Twitter and I think you could verify that they actually follow the call’s owner before they’re allowed to join? Otherwise this seems wide-open for trolls/bots, and kind of only half-anchored to Twitter.