The main part of Defen-Door is the camera. When pressed, or when one of the sensors is triggered, the wireless camera will turn on and alert the user via a Smartphone with a snapshot of what it sees. From there, users can choose to see the live video feed or send an audio message to the person at the door.The camera is water-resistant and can be used inside or out, depending on a user’s needs. This means it doesn’t have to function as just a doorbell, but it can also be used for something like, say, keeping track of when someone opens the refrigerator. A 150-degree viewing angle and 720p resolution round out the main features of the camera. It’s all powered by three AA batteries, which the creators promise will last about one year, or for 500 30-second recordings.