Here is another video doorbell that lets you see who is knocking on your door. The Momentum Knok WiFi Video Doorbell supports iOS/Android devices. It detects motion to send alerts directly to your mobile device.
The Knok has a 1080p camera with a 130-degree wide angle view. Users can customize rules and motion detection zones on their smartphone. They can also activate a 110db security siren. Free cycled cloud storage is also available.