Finally we got a hosted in sourceforge :)
After looking for the appropriate hardware platform I have a candidate:
MC13213 this device has a zigbee modem and a 8 bit MCU; development boards are cheap.
For Ethernet connectivity I'm looking for a good option a Coldfire chip; M5223x will be a good start.
From the software side FreeRTOS is a good option and they are some ports to this architectures so will be easy to use this RTOS.