Scientists Make Smartphone App That Performs Full-Body Motion Capture

They use IMU sensors not cameras. The linked article is a bit bad in that it does not make it very clear and it has a quite misleading hero image (in the tradition of useless hero images). They try to estimate pose in detail through IMU signals. While pose estimation through IMU is not new, I am not sure if something like getting into that deep detail (out of a general classification) has really been done.

Lens adjustment, sensor adjustment, this is a problem ripe for the deep learning "bitter lesson"

> just an enthusiast, not a scientist

Considering the anime character, it's 50/50. /s

This is not at all what they did here. Here, they use the IMU sensors in the phones, not the cameras. Using cameras is too restrictive if one wants to apply it to more real-life-like situations due to visual obstruction etc. They are not the first to use pose and movement estimation using IMU sensors by any means, but I guess it still is a valuable contribution to have a working-out-of-the-box app, and also they seem to get into estimating more details in the pose than just a general classification.