Google is launching its facial recognition video doorbell, the Nest Hello, in the UK to challenge Amazon's Ring.Initially released in the US in March, Nest Hello is the first of Google's new home security product lineup to make it to the UK, ahead of its Nest Secure alarm system.Nest Hello is a wifi-connected smart doorbell with a wide-angle camera that captures high definition HDR video with night vision after dusk. Its differentiating feature, however, is its machine-learning technology that analyses video from the front door, which Google claims can differentiate between people walking by, visitors or delivery people approaching and loitering burglars, only alerting users when necessary.When someone rings the bell, it sends alerts with pictures from the camera to the customer's phone, allowing them to talk to visitors from anywhere with an internet connection.The doorbell can also say three short phrases.