Sony's Exmor RS sensor already has hardware HDR, and can take HDR videos in real time. They should ship with many of the high-end smartphones this year.

http://www.dpreview.com/news/2012/08/20/Sony-Stacked-CMOS-se...

Skipping all the details, it's because you have a left eye and a right eye, not an up eye and a down eye.

The effect does not go away if you only have (or use) one eye.

Turn the mirror 90 degrees and nothing happens. Turn your head 90 degrees and it flips up and down.