Does the Google Nest Doorbell (battery) work with HomeKit, Alexa, and Google Home?
The Nest Doorbell (battery) cannot record 24/7 and needs the Google Home app.
It is an HD video doorbell that runs on its rechargeable battery or on 8 to 24 VAC doorbell wiring, and it connects over Wi-Fi. It suits Google Home users, with native support through the maker's cloud. Alexa and Home Assistant users reach it through an integration (the maker's cloud).
How the device gets into the platform on this route. The headline is the best route: local before cloud, direct before bridged, core before community. The methodology page lists every level.