These strange-looking things are called taiji (tai chi) rulers, not because they measure anything obviously, but probably because they keep your hands at the same spacing when you’re using them for qigong exercises.
They fit comfortably in the hands and can be held in different ways, depending on the exercise. They are excellent for gentle exercise for elderly people as well as for martial arts work, and they are very tactile.
It looks as though I shall be making quite a few of these. I’ve already sold two of the first three I made.
More of a writeup here.