The Arduino Wireless Shield allows an Arduino board to communicate wirelessly using a wireless module. It is based on the Xbee modules from Digi, but can use any module with the same footprint. The module can communicate up to 100 feet indoors or 300 feet outdoors (with line of sight). It 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. An on-board swith allows the wireless module to communicate with the USB to serial converter or with the microntroller.
Arduino Wireless Shield - XBee Shield - General Specifications
Allows an Arduino board to communicate wirelessly using a wireless module
Communicate up to 100 feet indoors or 300 feet outdoors