I think it would be necessary to place "sensors" inside. But I even if this would be possible, I don't think this would lead somewhere.
When I attended a seminar of Ikeda Hiroshi he enjoyed to not move one inch but to change "his inside" so uke lost his balance.
I have some uke who I can lead to a certain point and get to a position where I can throw them or not throw them without moving. I change inside. But also I don't think I'm "moving" inside. A sensor would stay in the same place. But maybe it would change it's "direction".
Also: Endo sensei teaches to lead one's feeling downward. This can not be shown. And this is not alone about the alignement of the body but also about directing the intent down, to the earth.
Maybe it would be interesting, to mark the vertebrae of the spine. Or some point within the shoulders, the hips. To see how all this opens/closes, twists ... But I don't think it would help.
It's almost like asking for a map of the feeling of "love".
The beauty of IS is that there is almost no outward sign of what happens. While you can see "love" on a person's face, or you can see "hate" or other things, the face in IS is calm and more like listening than projecting.
This idea is like trying to discern the inner paths of the body through a technological mirror of what can be seen of the outside movement. Only the human ki can follow the path of IS, and only the ki can give the mind access to those paths. And it can give us access to the inner paths of an opponent.
I met a 67 year old Chen tai chi man recently and he asked me to join in his class. Even though I didn't know the form well, when we finished, the man said I moved like I had studied martial arts. He approved and I could tell he wanted to show me some stuff later on.
Later the same week, I had an interesting experience. I was almost attacked by a roofing contractor who was running scams in the neighborhood. He realized that I wasn't going to hire him and he just showed up at my house and almost attacked me on my front porch.
Like BK Frantzis outlined, this guy was operating 100% on the animal level of fighting--getting himself all worked up with his hormones and adrenaline, while my concern was keeping myself calm and relaxed, upright, with my weight in my feet. I was very consciously directing my weight down. The only thing I did was get taller and calmer, but also more serious with him.
He acted like a somewhat trained boxer. He almost threw a punch and I realized that his intent was to hit my head and knock it back into the door frame, then follow up with a flurry of vicious punches and kicks. I'm sure he's done that to someone before. I just told him to get in his truck and go somewhere and calm down before he got into serious trouble.
I don't think he ever had any idea of what he was facing, but he could never get himself organized to throw a punch. It was a different kind of encounter, altogether, from things I've experienced in the past and it's entirely due to what I've learned over the past few years from Mike, Dan, Ark and Rob John.