The promise of a world with modular smartphones has just gotten a little more real, as Google’s Advanced Technology and Projects, or ATAP, has released the Module Developers Kit regarding its Project Ara smartphone. The Module Developers Kit, or MDK, is different from a Software Developers Kit (SDK), obviously, because instead of creating software to run on the smartphone, the partners Google’s looking to recruit would be making the actual physical parts for the Ara phone.

The MDK, it should be noted, doesn’t hold much for those of us who aren’t planning on creating modules for the Ara device, so if you don’t feel like diving into the 81-page document, don’t feel bad. However, there are some clues about how Google will bring the device to market, and the various configurations we may have available to us when that happens.

The main product Google itself seems to be planning is an endoskeleton that comes in a few different variations and sizes. So far, the document lists mini, medium, and large sizes for the device, all measured against a uniformly sized 4×7 grid of boxes:

In addition, Google is considering more than one configuration of that endoskeleton, with “endo-ribs” that go across different sections of the phone. The end result means that there are a lot of possibilities at work:

The document also outlines some important restrictions concerning the dimensions and features that module developers can play with. Moreover, there are also some exceptions to the dimensional guidelines discussed for special modules that do more than your standard RAM or CPU module. One possible idea floated by the document discusses a pulse oximeter module, which would measure a user’s blood oxygen levels, and later on the document shows off a possible thermal imager module—which is just about the coolest idea ever.

The document also explains more about how the electro-permanent magnets, or EPMs, would work in terms of keeping modules attached to the smartphone. The EPMs have “two selectable states: the attach state and release state, corresponding to high and low levels of magnetic force. Electrical power is needed to switch between the two states only; the EPMs require no sustained electrical power to maintain either state.”

In short, the document offers up a very interesting glimpse into what’s shaping up to be one of the biggest disruptions of the mobile phone market since the release of the iPhone. Apple’s handset showed that smartphones didn’t have to be mini-computers (exemplified by the then-dominant and business-preferred Blackberry). Imitators flooded the market, and soon everyone had powerful and stylish devices in their pockets.

Project Ara has the potential to similarly upend the conventions of the smartphone industry. If enough people decide they’d rather buy upgrades to their phones piecemeal, and embrace the customization offered by Project Ara, the age of the closed, unibody smartphone could come to an end.

Hopefully Google ATAP and its development partners can make good on the Project Ara promise, and can bring the Ara ecosystem to market by early 2015, as has been alluded to before. To be quite honest, I might even ditch whatever handset I have just to get one. Where do you come down on the modular smartphone idea? Will Apple and Samsung join the fray to compete, or is this going to be all Google?

[Project Ara MDK]