Update:
Digi.com says that their swappable 900 Mhz and 868 Mhz modules are  
accepted around the world.
( one or the other in each geographical location )
These are better than 2.4 GHz because of range considerations.

Look at the 900MHz Zigbee modules from Digi
http://www.digi.com/technology/wireless/products.jsp
Up to 64 km.
Unfortunately, policies for RF spectrum allocation vary across the  
world.
Gus




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