XBee is a radio module. Useing two of these modules data can be transmitted wirelessly. Using an Xbee shield can simplify Arduino prototyping life significantly.

Specifications

• Over-the-air baud rate: 250 kbit/s
• Transmission power: 1mW to 1W types are available, the higher the power, the higher the price
• Typical range increases with transmission power; 1mW – 100 meters / 1W 65 km (in open air, using good antenna)