i'v decided to do light detection method, but im wondering is there any way to do proximity detection with an arduino? could I use the same mechanics as the company that made the octolively kit and use both infrared photo resistors and infrared leds to get proximity sensing?
A quick google will list several Arduino projects that do proximity detection. http://bildr.org/2011/03/various-proximity-sensors-arduino/ shows IR proximity. Depending on how big the table is / how many IR detectors you need you may need to use some external hardware to multiplex the analogue inputs. A possible problem with using regular photo-resistors (Light Dependant Resistors) is the table would light up as the room gets dark and this light could effect the LDR. The probable reason they used IR is it will work in the dark and is less effected by visible light.