I don’t think we want our bodies to be UIs.
The assumption driving these kinds of design speculations is that if you embed the interface–the control surface for a technology–into our own bodily envelope, that interface will “disappear”: the technology will cease to be a separate “thing” and simply become part of that envelope. The trouble is that unlike technology, your body isn’t something you “interface” with in the first place. You’re not a little homunculus “in” your body, “driving” it around, looking out Terminator-style “through” your eyes. Your body isn’t a tool for delivering your experience: it is your experience. Merging the body with a technological control surface doesn’t magically transform the act of manipulating that surface into bodily experience.