Interesting modular smartphone concept, Motorola's Ara project could sooner or later find application in reality.
Ultimately it answers a pertinent question: "what if instead of purchasing 4 distinct types of devices (phone, tablet, phablet, watch) you could 'assemble' a phone by using it from time to time only once What parts are needed?

It's a innovative vision but sensible, which could revolutionize the entire smartphone market: the tendency to renew an 'obsolete' mobile phone every year or two would be replaced by the upgrade or replacement of individual parts, which could be resold or (why not?) recycled by same company.
A platform on which you they could graft even compatible parts made by other companies. A bit like Android has done for software, in other words creating an ecosystem of 'third parties', facilitating their access to development and accelerating the pace of innovation.

Ara would be a kind of chassis, a 'skeleton' on which to mount the various modules: extra batteries, various displays and elements that allow for more extreme customisation. In the next few months the project will leave embryonic stage to bring to those interested a real development platform: Let's see what the idea of having an "Open Source" smartphone will lead to.