The two Pixel handsets are the first mobiles to trigger Google Assistant by pressing their home buttons, somewhat like Apple's Siri.
The Home speaker lets the same artificial intelligence tool be controlled without use of a touchscreen. It rivals Amazon's Echo.
Google also unveiled new virtual reality kit and a 4K media streamer.
The Assistant has two key advantages over rival systems:
- it can hold a conversation, in which one question or command builds on the last, rather than dealing with each request in isolation
- it draws on Google's Knowledge Graph database, which links together information about more 70 billion facts, and has been in use for four years
However, the US company will have to overcome privacy concerns and convince users that chatting to a virtual assistant has advantages over using individual apps.
Google already offers the Assistant as part of its chat app Allo - but the software has been installed on only a small minority of phones that support it as yet.
Smarter phones
The decision to brand the phones with the Pixel name, rather than Nexus, marks a break with the past, and is intended to signify that they were designed in house rather than by another manufacturer.
The devices come in two sizes - with either a 5in (12.7cm) or 5.5in (14cm) OLED (organic light-emitting diode) screen - but otherwise have similar specs.
Google said the 12.3 megapixel rear camera they share was the best on the market - basing its claim on an independent test by DxO Labs. And as further enticement, it is offering unlimited storage for the photos.
Google also drew attention to the devices' glass-and-aluminium bodies, and specifically noted they featured a headphone jack - unlike Apple and Motorola's latest models.
Unlike most Android phones, the Pixel and Pixel XL will automatically install operating-system and security updates as soon as they are released.
But it is their ability to access Assistant as a standalone facility that makes them unique, at least for now.
"It goes one step further than tapping on the microphone in the Google Search app and getting a bunch of responses - it gives a conversational feel to what you are doing," Google executive Mario Queiroz told the BBC.
Users can, for example, ask for what films are playing at nearby cinemas, and then follow up the reply by saying: "We want to bring the kids," to narrow down the selection.
"Having a conversation - one where you ask a question and then follow-on questions - is a much more natural way to interact, and you would think that would offer a better user experience," said Brian Blau, from the consultancy Gartner.
"But we haven't had that type of system offered at the mass market level before, so it's hard to say how well it actually do."
The Pixel will start at £599 and the Pixel XL at £719 when they go on sale on 20 October.
Lighter VR
A month later, Google will launch the Daydream View.
The virtual reality headset and motion-sensing controller make use of Pixel - and other forthcoming compatible phones - as a display.
A near-field communication (NFC) chip automatically puts the handset into VR mode when it is fitted inside.
But the main advantages the £69 package offers a user over the existing Google Cardboard headset is a strap to hold it to their head and its wave-and-click controller.