Tangible Manipulation of Wirelessly Linked Objects
From the IAMAS Ubiqutous Interaction Research Group in Japan comes these nifty techno-dominoes.
Each block is capable of deciding which of its fellow blocks to knock over next. They do this by communicating wirelessly, thanks to internal zigbee radios. Once a block has received the signal to fall, it sends a message to the next block and so the process continues. Click through for a video where several permutations are demonstrated, and a glimpse of the potential of this application is revealed.

