Has anyone though about adapting the Open Outcry system that is used on some financial exchanges?
http://www.cmegroup.com/education/op...d-signals.html
It's basically a simple and clear method of nonverbal communication used relay information about extremely time-sensitive financial and commodity trades from across a very noisy trading pit such as NYSE. Since it's so simple and optimized for an environment very similar to an FRC event (where there is a lot of noise and time is of the essence), open outcry could be another useful option for spy communication.