[anoved]

Or what about using built-in motion sensors to record the relative camera location and orientation of a series of frames captured with an e.g. iPhone camera? I don't know exactly how the accelerometers and gyros work, or what sort of data they provide (linear distance vs just orientation changes?), but imagine holding down a "scan" button as you simply swing the phone around a subject to capture a series of images. I would think it would be possible to reconstruct 3d surfaces (at least under suitable illumination conditions, I guess) given known camera location/orientation for each frame. Pushbroom stereo, in remote sensing parlance...

[m_eiman]

Tracking movement in 3D using dead reckoning is apparently very inaccurate, with the iPhone sensors I wouldn't expect it to be accurate for more than a few seconds at best. I visited a startup working on the problem a few years ago, and they had problems even with dedicated hardware.