The Nexus Q was announced at their developer show in June, the best description of the device I found is that it is a “streaming-media device.”  Basically you can plug in any Android-based equipment and achieve functionality with your TV and speakers. 

The ball (it looks like a bowling ball) has a pair of speaker outputs, a Micro-HDMI output, an optical audio output, a Ethernet jack and a Micro-USB port.  Inside the ball there is a 25-watt amp, Bluetooth and dual-band Wi-Fi.

The Nexus Q will only support Google-based devices and content distribution sources (like YouTube; no Netflix.)  Primarily it can be used play your music or a YouTube video.  Apple’s AirPlay, on the other hand, works with many third-party apps.

The price for Nexus Q is $300, which is considered high for this type of technology.  Apple TV sells for $100.  The built-in amp is part of the reason for the higher cost, but Google is also building the device in the U.S.  That decision is credited with upping the price as well, although, that is also a nice marketing hook for them.