The engineers behind Project Ara are trying to make the last smartphone you'll ever need. Their design for a modular device has users slotting components — a camera, extra storage space, a Wi-Fi connector — into their phones, as and when they need them. It's an ambitious scheme, but engineers working at NK Labs in Boston have already produced a working prototype, which they showed off to modular smartphone evangelist Dave Hakkens during a recent visit.

The early model, called Spiral 1, is creamy white and boxy, and a far shot from the beautiful modular models shown earlier this year. But unlike those mock-ups, it actually works, and it looks to be more stable than the prototype shown at Google I/O in June, loading its Android OS past the boot screen. At the moment only half of the prototype's space is open to developers, but NK Labs says it has already improved on the Spiral 1: the Spiral 2 will use special Toshiba chips that will open up much of the phone's modular space for developer functions.

That new model will be shown off at Project Ara developer conferences in January, in both the US and Singapore. While Project Ara's design is not the next Google's Nexus — or even an official Google product — its creators hope that it could be the future of smartphones.