Is DuoLingo looking at adding OpenBadges? this allows you to create custom "badges" of completion inside of DuoLingo and publish the results for the individuals to the public via their "backpack".
Other sites are joining OpenBadges are was curious if it is even on the roadmap even your radar to look at.
This is an increasingly relevant question - support and recognition for OpenBadges is increasing: http://www.southampton.ac.uk/iliad/education-innov/open-badges-in-higher-education.page? and http://openbadges.org/participating-issuers/