We're just at the stage where we wish/hope the new kid will learn how to suck her thumb and self-soothe, but instead of giving her the chance, we usually seem to take the instant pacification route by plugging the pacifier back in.
So it's a bit of a stretch to imagine wanting to stop a kid from sucking her thumb. And it's beyond me to imagine wanting it so bad, you'd tie a freaky-looking thumb cage on her hand. [Apparently, you thread ribbons through the heart-shaped loops at the bottom, and tie it onto the kid's wrist.]
What I can imagine, though--because I've seen Crash, and a disturbingly sexy Rosanna Arquette getting down with her giant leg brace--is that this thing could have substantial long-term effects that the average toddler's parent doesn't even want to contemplate.
If you want to nurture your kid's fetishistic side, though, this puppy's on eBay for another three days.