I taught grade 5 students how to use Goodreads and told them if they wrote book reviews on their own I would award them a badge using Edmodo, a social network out school uses. I've had a torrent of reviews and am surprised that 72 of 158 students have responded by writing a review. Several have written 12-15 reviews in four months. I know there is an app called, Foursquare, and I don't know if it could be used in the same way as Edmodo, but I think so. Obviously, you could use this in many different ways as a librarian. I think it is hard as a specialist to make a connection with students because of the time constraints and this is just one tool to help bridge that gap.
Hyperlink to this great article that presents the pros and cons to badges. Make sure you read the comments - it's a terrific discussion!