Need a Wireless communication? Use the Xbee
If you are looking for a wireless solution to a communication problem, the Xbee modules might be the answer. These modules can be used to connect an Arduino board, like the Mega version, to a computer or another board to create a mesh network. There is a long list about network based applications you could do. Here is good gallery that will stimulate your creativity.

Just think about a network that allows you to exchange data between all the connected devices. You could control and track an Arduino program wirelessly, send sensors’ data to a computer running a Matlab program for complex tasks and send the results back to the board.
In this tutorial we will setup a basic network using two Xbee modules in order to exchange data between a computer and an Arduino Mega.