What is the function of Duplo part# 38507 RAIL ACCESSORY, NO. 4 Can someone explain to me what 38507: RAIL ACCESSORY, NO. 4 (#6225519) is for? I've got this in the new  Duplo Train accessory #10882 and can't figure out what it does :S
It's an interactive piece that makes the train perform a cool(ish) function when it rolls over it.


The train has a sensor on the bottom that reads the piece and does the deed.


When the train reads this red one... it stops moving, which is sorta coolish  for a jealous older sibling maybe ;).


Watch 3 videos explaining all the cool possibilities.  (1), (2), (3).