What other options are there for the hardware implementation of the task of determining the position of points in space?

Question

Electronics

It is necessary to find the position of three points in space, relative to the reference point. Example: There is a robotic arm, determine the position of the "brush" and the ends of 2 "fingers". I do not want to use "surveillance tools" such as: a camera, an IR sensor, and the like.
Ideas (relative to the example):
- install the accelerometer at each of the points
- install the accelerometer in the hand, and determine the position of the "fingers" by the cables attached to the ends of the "fingers" and the angle of rotation
Actually, I wanted to know other options for implementing the task using this example, which I missed.

Answer 1

I realized that I was not allowed to ask questions at night. I don't know how to edit, but something is wrong with the ideas. But I would like to know how you can do something similar to the one described above?

Answer 2

If in relation to a robo-hand, then I think you can use encoders as an option .... Well, if you want to get very confused .. then you can try using the theremin idea