Wireless Controller to Controller link

I tried to search for this, but get flooded with wireless microcontroller to PC/Phone discussions.

I want to build a wireless network between Arduino (or any microcontrollers) boards with no need for any external components.

The reason for this is portability. I will be designing numerous demonstration apparatus which I want to be able to take with me to any location I need and have them function properly.

One demonstration I can think of already which I will implement this capability on would be a "Shoot the Monkey" demo. This requires that I send a signal to fire a projectile at the same moment I drop a target.

Currently I use a photogate to detect the projectile firing and a very long phone cord to carry the signal. I would like to upgrade to the point where my launcher and my target each have a microcontroller attached to them, and when I press a button on a third microcontroller handset, the projectile launches and the target drops.

So... how do I link multiple microcontrollers to their own wireless system to obtain real time data exchange between components? Could the Arduino Yun establish an ad-hoc network with another Yun?

Really I would love if the TinyDuino could be used to do this so I could add wireless communication to small components if needed.