Google's Project Tango isn't a real product yet. It's a science project.
Using advanced cameras, sensors, and processors, Project Tango aims to allow phones and tablets to record a 3D view of the world around them, and understand their precise location and orientation in it.
Google announced a developer tablet powered by Nividia's Tegra K1 chip almost a year ago, but access was by invitation only. A month ago, Google made it a little more widely available, and dropped the price in half (from $1024 to $512—Google loves developer inside jokes like power-of-two numbers).
Now, you can buy the development tablet direct from the Google Store, with no invitation needed.
The story behind the story: This is either Google moving off excess inventory, or preparing to push this project further into the mainstream by "priming the pump" with development projects. If tablets featuring the Project Tango technology are to go on sale this holiday season, or early next year, there will need to be hundreds of developers working on software to take advantage of the technology.
We may hear more about Project Tango and Google I/O this week.