There are a couple of different ways to make your Arduino wireless.
XBee
XBee radios have become very popular in the Arduino community because they are relatively easy to use, they are very robust and have a long range of operation.
There are basically two types of XBee radios – Series 1 and Series 2 – the two types cannot communicate with each other. I collected here the most important differences between the two. For more detailed explanation, see this document from Digi. Or read this site from Sparkfun.
Series 1
- Easier to use and configure
- Can simply be used to replace the usb cable on the Arduino
- For point-to-point or star networks
Series 2 (or ZB or 2B)
- A bit more difficult to set up and configure
- For mesh networks (or whatever else you configure them to do)
- Can’t communicate with the Series 1 modules
Links
- A gallery of XBee projects collected by Digi, the company that makes the XBees
- Building Wireless Sensor Networks (Book)
Wifi
http://arduino.cc/en/Main/ArduinoWiFiShield
Bluetooth
http://medialappi.net/lab/equipment/wireless/bluesmirf-gold/
Batteries
Sending data wirelessly is not always enough. You often want to make your whole project completely wireless with the help of batteries. You can use a 9V battery with your Arduino, but LiPo batteries have better capacity.
Arduino Fio
Arduino Fio is a version of the Arduino board that comes with a socket for an XBee radio and it also has a charger for LiPo batteries.
How to configure Fio for Xbee.