Here's a link to a youtube video of two robots each with two bricks using blutooth communication. http://www.youtube.com/watch?v=2IjkocRiASA
The two builders and programmers are 13 year old students.
They created dance robots for the Robocup Junior competition in Australia.
They use bluetooth messages to start the programs running on each brick with the push of one touch sensor. This ensures all 4 bricks are running in time with the music.
They also use messages within the 4 programs to ensure the robots are synced.
They spent many months and learnt a lot preparing for the competion.
One of the discoveries they made was that with the master sending messages to three slaves, there needs to be at least 1 second between each message being sent to a different brick. This is so that there is time for the Master to change channels. This frustrated them for a good amount of time before they figured it out.
It all looks so simple when you watch the results.