How to measure the distance between 2 points accurately
want to measure the movement of 2 points on a material surface as it is stretched and released the points move apart and towards one another. The points are real and tangible. This of pins in cloth and we want to measure the distance between the pins.


If the two points can be made then you could use an Ultrasonic range finder. you could have one point be a wall (use balsa wood or something light) then the other could be the range finder. You might have to do a little bit of engineering for attaching the range finder to the pins on the cloth, but I believe it's doable.

heres an amazon link for a generic arduino range finder: http://www.amazon.com/RHX-Ultrasonic-Distance-Measuring-Transducer/dp/B00F6KLLGG/ref=sr_1_2?s=electronics&amp;ie=UTF8&amp;qid=1439459256&amp;sr=1-2&amp;keywords=range+finder+arduino