For those who came in late, Project Tango was the company's first attempt to bring a solid augmented reality experience to the average user. It used an array of cameras and sensors to accurately map 3D areas.
While the concept was not bad, the fact it needed so many cameras caused the devices supporting Tango to be relatively large and expensive.
The first Tango device put into production was the "Peanut" phone, which was given to early access partners in 2014. This evolved into the "Yellowstone" 7-inch tablet, which was initially sold for $1,024 before a massive price drop to $512.
The only other devices with Project Tango were the Lenovo Phab2 Pro, which was a pretty pants phone in the first place. Then the ZenFone AR was released to a loud sounding yawn.
Google is working on a software-only solution called ARCore. Not only is ARCore similar to Tango in functionality, but it doesn't require specialised hardware.