This app has a similar model, however, not based on mutual teaching, but on the concept that everybody mentors someone who is less advanced: http://www.understudyapp.com/ As far as I know, it didn’t take off though.
This app has a similar model, however, not based on mutual teaching, but on the concept that everybody mentors someone who is less advanced: http://www.understudyapp.com/ As far as I know, it didn’t take off though.