There are a number of ways you can "sense" things and depending on what you want to sense, you would use different sensors. From the video in the link, it looks like the panels have banks of 5x4 leds that are activated by 1 sensor. In this case it is probably a IR transmitter/reciever Optical Detector / Phototransistor - QRD1114 - SEN-00246 - SparkFun Electronics that can detect when something passes over it by the amount of light that is reflected back into the reciever. You could also use more powerful versions like a sharp proximity sensor or ultrasonic sensors, these would allow for detecting objects at longer ranges. You could also use capacitance if ou actualy wanted to touch the pannel. However if you give some examples of how you would use this, a more precise sensor could be recomended.