Apple's iPhone 7 Plus decided to add another lense to be able to make better pictures. Meanwhile Walabot who started with wanting to build a breast cancer detection technology released a 600$ device that can look 10cm into walls. Thermal imaging also got cheaper.
I think it would be possible to build a 1500$ device that could combine those technologies and also add a laser that can shift color. A device like this could bring medicine forward a lot.
A lot of area's besides medicine could likely also profit from a relatively cheap 3D scanner that can look inside objects.
Developing it would require Musk-level capital investments but I think it would advance medicine a lot if a company would both provide the hardware and develop software to make the best job possible at body scanning.
We have had cheap bathroom scales measuring body fat percentages (not terribly accurately, but still better than guessing from the BMI) for a while; if those didn't "move us past the BMI", why do you think a device two orders of magnitude more expensive would?
Cheap scales don't measure body fat uniformly. They ignore arm composition. For the purposes of standarization they give different answers than the expensive devices used in clinical studies.
Fitness studies also measure more than body fat. They measure the circumference of various body regions. I don't think a measurement that doesn't take into account the shape of a body produce a good answer.
Most medical devices that set standards aren't very cheap. Very cheap devices give nobody an incentive to run the studies