I've successfully used an HCS12 microcontroller with ZigBee (802.15.4) to program a robot controller before (did it as a project in a digital systems course

). Speed was almost as good as with wired serial. One PC would connect with serial to one HCS12 and transmit - the other is connected to the RC and simply buffers and passes through the data.
So...if you happen to have two HCS12s with ZigBee hardware lying around - go for it?