The Module Developers Kit (MDK) defines the Ara platform for module developers and provides reference implementations for various design features. The Ara platform consists of an on-device packet-switched data network based on the MIPI UniPro protocol stack, a flexible power bus, and an elegant industrial design that mechanically unites the modules with an endoskeleton. Throughout 2014, the Project Ara team will be working on a series of alpha and beta MDK releases. We welcome developer input to the MDK: either through the Ara Module Developers mailing list/forum or at one of the series of Developers Conferences.
These phones will be crazy flexible in their design - and they look pretty good too. I don't know if it'll be a small niche or a runaway success, but I definitely appreciate them for trying to do something different.