Sensor for 3D object

For my final major project at university I am creating an installation that users can interact with using a physical object to trigger a digital video on screen.
Any suggestions on what sensor would be best to use for this?
Ideally, I want the interaction to enable a digital response on the screen by touching the object and then whether it would be possible to add light? :o :-\

A touch sensor perhaps? Have a search for "Arduino Capacitive Sensor" and have a look here for some background: http://playground.arduino.cc/Main/CapacitiveSensor?from=Main.CapSense

It would help if you could explain the project in more detail, like what the 3D object is, is it fixed or mobile, what are the lights for, etc.

It all sounds fairly easy provided you're using something that isn't Arduino for the video stuff.