This is fascinating, but I'm slightly concerned about how 3D printing would work for this function. Many of the ones linked to are made from coiled wire, which gains certain material properties in the process of being drawn out, including part of its springiness. The Shapeways page about how they print stainless steel suggests it's a fairly loose-sintered steel matrix that they then infill with bronze, and that will have different material properties. I mean, I don't know how different, or how important the springiness is, but the way many of those shapes are coils and loops makes me think the spring is important? (Though, actually, I've just watched a video on the Beautiful Splint company's site and given the way they make their rings, it looks like it isn't and they're solid. Okay.)

Hmm. Sounds plausible from a materials/printing point of view, then, but then there's the expertise to know how to make them the right size given measurements of a finger. I note that all the companies involved in this are heavy on the jewellery expertise... Is it worth looking specifically for jewellers with an interest in 3D printing?