I spoke to a guy a while back who had one of these. They work by suction. The base is very close-fitting and made of latex, which has a slightly sticky texture. The idea is that you apply it, squeeze out all the air, and it sticks like a contact lens. I think that idea works, as far as it goes. But the base is quite thick by comparison with a lace or thinskin piece, so the hairline is not that good, and the manufacturing process is labour intensive and has to be done where the customer is, so it's expensive. Here is a video of one showing the manufacturing process:
To me it seems clever but a bit gimmicky - fixing a problem that doesn't really exist, for me at least. Also, I would be a bit nervous about wearing a piece that was just attached by suction. It won't blow off, but if someone grabbed it the right way it would peel right off. But I guess if you are allergic to glue and tape, you want a high density look with a covered hairline, and you have money to spend, it might be worth investigating. The guy I talked to was planning to switch to a conventional lace hairpiece.