Project Ara Demoed At Google I/O 2015 Live 

 Project Ara is the codename for an initiative that aims to develop an open hardware platform for creating highly modular smart phones. The platform will include a structural frame or endoskeleton that holds smart phone modules of the owner's choice, such as a display, camera or an extra battery. It would allow users to swap out malfunctioning modules or upgrade individual modules as innovations emerge, providing longer lifetime cycles for the handset, and potentially reducing electronic waste. Project Ara smart phone is scheduled to begin pilot testing in the United States in 2016 with a target bill of materials cost of $50 for a basic Grey phone.
The project was originally headed by the Advanced Technology and Projects team within Motorola Mobility while it was a subsidiary of Google. Although Google has since divested Motorola to Lenovo, it retained the Advanced Technology and Projects group—which has since worked under the direction of the Android division. 

We will have to wait until at least 2016 to see Google's much-anticipated Project Ara modular smart phones hit shelves as the company has announced a delay.
The Project Ara team at the beginning of this year had announced it would launch the modular smart phones this year in Puerto Rico as part of its pilot program. The team however has now confirmed that its phones will not launch until 2016, alongside announcing a "pilot market re-route" to a few locations in the US instead of Puerto Rico.