It's a bit more than a set of rollers, although perhaps not a whole lot more. It's the functional portion of the iPhone image copier, and it will be the core film handling element in any new product that IP chooses to design around it, such as a new instant camera.

The FPU is described here:

I don't have an iPhone and I likely never will. I like instant cameras, and that is why I'm interested in this product, and hope it sells very well. I want this product to make lots of money for IP so they can invest in more R&D and come out with new instant film cameras, hopefully ones with hiqh quality optics, and with selectable automatic exposure or full manual modes. Autofocus and auto-exposure would be desirable for most people. A high end interchangeable lens manual focus camera with either a Leica M-mount or Nikon mount would be great too.

If the iPhone printer sells well, then IP will sell more film, and the costs per image could come down to the point that more people will be able to afford it, which may spur further development and more users, and so on.