You can just make out the distance sensors as black rectangles on two of the petals. These let the flower track an object by rotating the flower stem. But if they determine the object is getting a bit too close for comfort, the servo motor on the back of each petal will cause the flower to suddenly clamp shut.
The video after the break starts off with an in-depth look at the hardware that went into the project. An Arduino clone called the GRoboduino makes this project a lot easier since it has a bunch of extras on the board aimed at things like sensors and servo motors. The mounting technique for the petal-powering-servos is quite attractive, and we enjoy the Snapple lid (probably not the actual brand but you get the picture) which has been coated with yellow felt for the center of the bloom. The final look is normal enough to fit in with home decor, but it still has enough geek in it to melt our hacker hearts.