I am wondering if there is a way to measure distance between two movable points (e.g., the first point is on the hand and the second point is on the back of the human body).
I was looking at different types of technologies. I found ultrasonic sensors but those need a reflective object and this does not work with my idea. I thought about separating the transmitter and the receiver but there is the human body (hip) between those points and it can not be face to face. I considered technology based on magnetic fields so it can be measured regardless of obstacles or motion but I did not find anything close to what I want. And for infrared it needs to detect some object.
Is there any technology that can help me achieve this type of requirement?