The DoorBird is the best recommendation and top pick for most versatile Video Doorbell. Unlike most competitors DoorBird offers ONVIF output which is a standard streaming protocol for IP cameras. This means with the proper equipment you can record your video doorbell 24/7 on an existing camera system capable of viewing/recording IP cameras.
The DoorBird has its own app and an API meaning it can integrate with a larger control system such as Control4, Crestron or URC. However you could also use it as a stand alone video doorbell. Best part of all this is there’s no monthly fees required!
From the Manufacturer:
DoorBird stands for the combination of exclusive design with innovative IP technology in the field of door communication. Our products are made from precious metals and manufactured in Germany according to the highest quality standards. The design is pure, straightforward and smooth.
Due to the consistent development and application of IP technology DoorBird products are top notch in the industry. In terms of quality, speed of push messages, voice and video, DoorBird IP Video door stations are the leader when it comes to innovative technology and design. Because of our specially developed encoding, packaging and transport technology, only 450 KBit/sec are needed for an excellent audio and video quality. DoorBird works reliably even if your smart device has only moderate internet connection.