Have you ever built a domino trail and then accidentally made them all topple over? Jarashi Suki and the IAMAS Ubiquitous Interaction Research Group developed a cool set called Esper Wireless Dominoes. The dominoes independently fall over and wirelessly trigger the next in order.
The video clip shows the many different ways Esper Wireless Dominoes can be used. This is a great toy that you could use for hours on end -- if you have the patience!