Silence is golden—or perhaps gestures are. At least, gestures can fill an awkward silence and control an app that whispers reminders in your earphones.
In this chapter, we built our first Android app with OpenCV's Java bindings. We also learned to use optical flow to track the movement of an object after detection. Thus, we are able to recognize a gesture, such as a head moving up and down in a nod.
In the next chapter, our project deals with motion in three dimensions. We will build a system that estimates changes in distance in order to alert a driver when the car is being followed.
