1. Three AA batteries work for a year. Just put it wherever you want. 2. HD/720P resolution with 150° wide angle lens, clearly know who is in front of the camera. 3. Two way audio with special echo-cancellation technology. 4. Waterproof design can let you put it indoor or outdoor; sunny or raining. 5. Vibration sensor to detect whether someone move your window, door, treasure box or any item stick with vibration sensor. 6. Motion sensor can be automatically enabled once DefenDoor notices that you are out. 7. Beacon technology supports to monitor whether or not a child came home from school on time. 8. Different ring tone by each phone.