If you are looking for a compact, rugged, and cheap sensor filled package there is nothing better than a Wiimote. This Wiimote was Hacked to Analize Tennis Serves. It’s great that there is an abundance of creative people working to make interfacing to devices like the Wiimote a bit simpler than it could be if everyone was starting from scratch.

Via: Hack a Wii

"So if you are a real nerd or a high school physics teacher and you want to try this you will need:
 

• A wiiremote
• A laptop with bluetooth
• C# or Visual basic from MSFT
• Johnny Lee’s Wiimote libraries http://johnnylee.net/projects/wii/ (you will need to modify a few lines of code to write the accelerometer data to a text file)
• A tennis ball wrapped in aluminum
• Bandage tape to tape the wiimote to your arm
• Thin speaker wire
• Graphing software"