Here’s an interesting article showing how to interface a common laptop touchpad with an Arduino. Metku’s project connects the Data, Clock, +5 V and ground connections on the touchpad to Arduino Pins 5 and 6, and power connections. Sample code is included, and the Arduino/Wiring library provides the necessary codehooks.
In the video they demonstrate using the touchpad to control LED patterns through a MAX7219 Led Controller, which requires the Arduino LedControl library.
Via Instructables.