I read a study some months ago, about students who gesture while learning - the first study I read related to language. Today, I read a similar study http://www.sciencedaily.com/releases/2007/07/070725105957.htm
but this time, dealing with maths problems, also indicating the positive role of gesture in learning.
The study related to hand gestures and speaking is here:
Language aquisition and mathematics have a certain synergy, so this is not surprising.
I'm not sure how to codify gesture into a language learning class, but with a small amount of thought, it could be integrated into the learning.
It would be interesting to split a class, and have one group use gesture while speaking and reading, and the other not, and see which group progresses faster. This could be done over the space of a week, and the class tested to assess progress, or over a longer term period.
The results would be publishable, if the study were set up properly.