Digi International has an extended-range RF module designed for ZigBee mesh networking.

Designated the XBee-PRO ZNet 2.5 it provides up to a mile (1.6km) RF line-of-sight transmission, which is expected to extend the range ZigBee mesh networking.

It is a fully compatible, pin-swappable extended-range counterpart to the cost optimised XBee ZNet 2.5 which provides up to 400 feet RF line-of-sight transmission.

The XBee-PRO ZNet 2.5 operates on the 2.4GHz ISM band making it appropriate for use worldwide.

See http://www.digi.com