There is a project in the Atmel Spaces that appears to have made it possible to use one of these with the Arduino IDE, specifically for these 3 modules:
ATmega256RFR2 Xplained Pro
ATZB-256RFR2-XPRO
ATZB-S1-256-3-0-U
Each of these runs $29 in the Atmel store. These ARE NOT anything like an Arduino format though... but it gets you a lot of the ways there. I suppose somebody could use the module with a custom-designed shield to make it fit the Arduino format completely.
Here is the link to the project in Atmel Spaces:
https://spaces.atmel.com/gf/project/256rfr2arduino/
Here is the link to a narrowed search in the Atmel store:
http://store.atmel.com/SearchResult.aspx?q=gsd:c-100118_m-60354