thanks for the reply.
The actual application is two robot 'tanks' in a circular arena, which each have an infrared beacon on top of them.
The sensors on each robot allow it to tell if it is looking at another robot(infrared photodiode), and how far away it is from objects such as walls, and other robots(Sonar).
so separating them isn't really an option.
The only solution i can think of is to somehow allow one robot to take control, so that only one robot can fire it's sonar at a time, and they would stay synchronized. i think a wireless system is just overkill.