According to the Wall Street Journal, Amazon is working on making not one, but two smartphones. And one of them will have some kind of awesome quasi-holographic glasses-free 3D display. That sounds like the kind of 3D people might actually want! The other one is... a phone of some kind. That's literally all the detail that was provided.
The one you're actually interested in, though, did come with a few extra tidbits about this glasses-free holographic voodoo magic. The Journal's sources claim that the phone will use "retina-tracking" technology to display an image that appears to actually float above the screen at any angle, and that this technology may also allow navigation of some parts of the phone using only your eyes.