jpsOneEye Stereoscope is now a product
 

After several hours of testing on various media setups the jpsOneEye
Stereoscope has proven to deliver defect free performance
comparable to free viewing without eye muscle strain.
With swivel base that rotates 90 deg the Stereoscope can be quickly
configured for parallel side by side or above and below stereoscopic
viewing mode.
Quick mirror angle set means no need to take it off for normal viewing.
Tested driving a car for several hours.

Mathew Orman

tyrell 3-D Hardware and Software Store

I don't understand what this does... can you explain what use it could have?

It's for viewing 3D images and videos that are presented by placing the left and right eye views either side by side or above and below each other. It is from what I can tell a pair of mirrors that you adjust so both images merge when you look at them. Traditionally with side by side images you would view them by looking at them cross eyed. This device means you don't have to go cross eyed.

Still looks very "Heath Robinson" to me.