Recommendations for the Duolingo Team
I feel that the ability to challenge a friend or group member to see who could achieve the most XP in a specific amount of time would introduce an element of competitiveness that could motivate people to practice more.
The idea of watching your friends progress and sharing it is nice, but the action of requesting a timed duel or challenge adds an aspect of urgency and competition. Unlike looking into someones progress, which in my opinion is more leisurely, the notification of a win or loss, and possibly the ability to view ones stats in such challenges is more personal, and may inspire an elevated sense of dedication to the task.
In the App: use clubs
In the web version: use Friends
Another recommendation would be to offer a hands free version that implements verbal lessons such as asking you in your native language and requesting that you respond in the learned one.
Duolingo - (Audio) "Which of these words means 'five'? Say : Ett, fem, ni, or ti"
Student - (Speaks) " fem"
Duolingo - (Audio) "Correct. Would you like to hear it used in a sentence? Say: yes or no"
Student - (Speaks) "yes"
Duolingo - (Audio) "Jeg har fem hester. This translates to 'I have five horses.'"
An addition to the program such as this could be the beginning of an accessibility application for blind students. It also allows people to study language in a more natural environment - listening and responding. Another application for this concept is the ability to learn while your hands are busy, or when it is unfavorable to hold something, but your mind is not completely occupied. Some examples of these situations include: cleaning or doing dishes, driving, basking in the sun, biking or other exercises, cooking, etc.
Both your suggestions are wonderful! An xp challenge would be great fun/learning in a more competitive way, and hands-free Duo would be excellent for blind students and doing lessons while driving alike! I drive an hour a day, I'd love to spend that time practicing my Spanish :)