I am currently working on a robust master/slave protocol but the NXTBee is capable of much more. You can communicate between up to 16 nodes in total, paving the way for swarm robotics.
If you’re keen to to play with them as well, mosey on over to the Dexter Industries shop where you can procure a few freshly made ones: [LINK]. If you already have an XBee and just want the interface board, you can get that here: [LINK]. For people who want MOAR POWAR, you can get yourself a Pro version right here: [LINK].