This chapter explores the wireless networking tools that enable two or more Arduinos to talk together. Chief among these is the XBee, an Arduino-friendly wireless module capable of connecting a whole network of microcontrollers. In Figure 4.1, you can see one of my own projects, a LEGO robot controlled with Wii nunchucks connected to XBee-equipped Arduinos. You can learn how to build it in my book, Make: Lego and Arduino Projects (ISBN 978-1449321062). After you get up to speed on the XBee, you will tackle the third project, a wireless doorbell!