I used this app in the last week of term..in an observed lesson! Students had drafted a letter in Spanish to one of the three wise men (Spanish tradition) and they then recorded this using the chatter pix app and posted on edmodo. They then listened to another and had to identify what gifts were being asked for, seeing if they could get all three details ie item, brand, colour or other adjective.
The app works by drawing a line across a mouth on a picture, then recording student voice and saving to camera roll as video. Great fun, and of course when students know their work will be listened to by peers, greater effort is put in to make something accurate and impressive!