Looks small enough http://www.primesense.com/solutions/3d-sensor/ (see "embedded" photo at bottom). Apple can probably help miniaturize it further; also process shrinks.

New input devices open new possibilities. Just vaguing: 3D sculpting; with the device propped up, any surface is a keyboard; 3D photographs.

Ideally, couple it with a holographic display...

EDIT mobile applications "augmented reality gaming, virtual shopping, Real View™ measurements, 3D scanning and printing, photography enhancement" (http://www.primesense.com/market/mobile/), engadget article (http://www.engadget.com/2013/05/15/primesense-demonstrates-c...)