It's an orb-like streaming-media device with a $300 price tag, that looks to act as the bridge between Android tablets and smartphones, and your TV. The (currently unlisted) YouTube video shows off its ability to integrate with your Google Music account, as well as "push" videos to your TV, similar to Apple's AirPlay functionality.
While it's not entirely clear from the product shots currently available, the Nexus Q has a micro HDMI output (and includes an HDMI cable), in addition to an optical audio port, Ethernet jack, and banana jack speaker outputs. The Nexus Q also has a built-in 25-watt amp, which means you won't need a separate AV receiver to power speakers, similar to a Sonos Connect:Amp. There's also built-in Wi-Fi, Bluetooth and NFC support.
The Nexus Q runs a version of Android 4.0, with 16GB of onboard flash memory and 1GB of RAM. Unlike streaming media boxes like Roku or the Apple TV, the Nexus Q only supports a few Google-centric apps: Google Play Music, Google Play Movies and TV and YouTube. The "social" aspect of Nexus Q initially appears to be the ability for multiple Android devices to create a group playlist.
According to the product page, the Nexus Q should be shipping in 2-3 weeks. Also listed is a set of $400 bookshelf speakers, made by Triad Speakers, designed to be used with the Nexus Q.
This is a developing story and will be updated with more details shortly.