The Xbee shield allows an Arduino board to communicate wirelessly using Zigbee. It is based on the Xbee module from Digi (formerly MaxStream). The shield can be used as a serial/usb replacement or you can put it into a command mode and configure it for a variety of broadcast and mesh networking options.
The shields breaks out each of the Xbee's pins to a through-hole solder pad. It also provides female pin headers for use of digital pins 2 to 7 and the analog inputs, which are covered by the shield.
Digital pins 8 to 13 are not obstructed by the shield, so you can use the headers on the board itself).
XBee is a modified ZigBee protocol.
***PLEASE NOTE - THIS SHIELD DOES NOT COME FITTED WITH AN XBEE MODULE - THESE MUST BE PURCHASED SEPARATELY***
A large range of series 2 (2.5) or series ZB Xbee modules are available for purchase including modules with external antenna connectors, and modules with ranges of up to 1 mile! You can find them here