As someone in another comment already pointed out, YC previously funded a company called "Verbling" (https://www.verbling.com https://www.verbling.com) in their

As someone in another comment already pointed out, YC previously funded a company called "Verbling" (https://www.verbling.com https://www.verbling.com) in their Summer 2011 batch whose original selling point was to provide an instant, one-click 1:1 pairing of language learners with native speakers via videochat. I'm not sure how well that concept caught on though... And if you check out their website, they seem to have pivoted to a more traditional "livestreamed language classes" model.