Take a 4x5" camera, with a 4x5" back.
Put on this little adapter, and instead you can put on a Leaf or Phase One digital MF back.
Take a photo, slide it across the back, take another, etc. Take all (5, 10, 20) of those photos, stitch them together, and you've got a 4x5" 1 GigaPixel (or so) image (and hopefully nothing moved and the lighting didn't change between shots).
That's the adapter, I think they're selling a camera body as well.
Nothing new, really, Alpa have been selling shifting-backs for years...