This is a cool product at a very reasonable price: $30.
The device offers a 1080p HD smart home camera with 14 days of free rolling cloud storage, wide-angle lens, two-way audio and the ability to send alerts to your phone. You setup the device to use a local wifi network and control it via a smartphone application.
I have long wanted such a product (they have been available for a few years but haven’t been cheap) and now they are available at a great price. The main drawback I see is that it requires a power connection (it doesn’t have a battery option). So setting it up as a doorbell is a bit of an issue (you have to get power to it somehow).
Order your camera. Learn more about the device from Wyzecam
Related: Camera Trap Images of Very Rare Wild Cats – Answer Your Doorbell with Your Smartphone Wherever You Are (and see video of who is at the door) (from 2015 – Video Cat Cam – Canon PowerShot SX60 HS Digital Camera