I was introduced to this concept decades ago when I was in Japan attending school for a couple of semesters.
I would love to build something like this for my computer table. I don't mind the house being on the cooler side in general (although nowhere near as cool as some permies seem to like it, as I would turn into an icicle), however when I need to spend time at the computer, my feet tend to get too cold.
This totally fits with the concept of "heat the body, not the room" and the article does stress the need to put fire safety first. It is important to remember that even low heat if left drying
wood for a long time, can make wood more flammable. It's more complicated than that, but I'd need one of our more knowledgeable on the subject permies to explain it.