In Chapter 10, Obstacle Avoidance and Collision Detection, we saw how to use the MaxSonar rangefinder. If we attached the rangefinder to a servo motor, which we saw in Chapter 16, Servo Motors, we could create a proximity sensor that could rotate up to 180 degrees to monitor a large portion of a room. When the proximity first starts up, it would need to run through an initial cycle to map where the objects are, to begin with, and then monitor if anything changes after the initial run. If the proximity sensor does detect that something is closer than it should be, it could play an alarm through a speaker as described in Chapter 12, Fun with Sound.
These are just some of the projects that you can create with the Arduino. Now for your last challenge.
