It's called openKMQ / openOverUnder and uses a cheap prism viewer (available since 1983) that allows for full color stereoscopic viewing of printed matters as well as LCDs.
The iPad is the first tablet class device that seemlessly works in portrait mode and is therefor a perfect match for the over/under viewing method.
The catch with the viewer is that one has to keep it at a precise distance to have a 3-D experience. This sweet spot distance is proportional to how far the pictures of right and left views are apart. The bigger the image pair, the bigger the optimum viewing distance.
A minimum size would be a postcard, so sorry this won't work with an iPhone, but you can alter the proportions so it fits any remote controlable Digital Picture Frame.
For the iPad, using the full screen (half/half), the optimum distance is 440 mm.
Step 1: Get the Viewer and the HDF Plate
For sources in other countries look here.
Get High Density Fibre HDF measuring 600 x 425 x 3 mm (or 3.2mm)
The pics show one that is painted black on one side.
Find a laser cutting service or a wood CNC shop that can process the EPS / SVG files.
Step 2: Assemble It
Step 3: A Recommended Bag for Your IPad3-D Accessories
It also has several inner/outer compartments.
More about it in this blog entry.
Step 4: How to Prepare Images for the 3-D Experience
You definetly need true stereoscopic image pairs.
Create a 768 x 1024 pixel image file (PNG is best), background color should be black.
Place the right view centered to the upper half, and the left centered to the lower half.
I'll soon publish a software that creates those as well as 3-D PDF files that can be viewed with iBook. Keep an eye on this blog.
I also prepared some 3-D videos (786 x 1024) and imported them with the Apple Camera Connection kit. It works as long as you place them in the DCIM folder of an SD card or try an USB stick with such a folder. But these were done with a professional compositing program.
I hope to get some help with a cross platform solution or a quick AviSynth script.