For this project, you will need a Nintendo DS touch screen as well as a breakout module. The latter is essential as the output from the touch screen is a very thin and fragile ribbon connector, and it will be impossible to interface to the Arduino without additional components.
Nintendo DS touch screens are inexpensive and can be obtained from many suppliers. The XL version is about twice the size of the standard version; this is the recommended unit, if you can obtain one. The breakout module is from Sparkfun or their distributors.
|Nintendo DS touch screen|
|Touch screen breakout|