Triggering events through collision in Unity 3D

I found this very interesting

http://www.youtube.com/watch?v=5KKKS0O9laY

Dealing specifically with triggering an event (a movie in our case) by entering into a 'hit' area in the player. It is collision detection but it serves our needs as it allows for spawning a movie textured plane to  on entering the 'hit' sphere and destroying on exit.