New component? tubing with sensor-detect length

Hi just wondering if there is a strip of some sort, say 5 ft long, where detection can get recognized. example: if items are placed at 5 ft 3ft and 1 foot the I can detect via something or 2,ft 1,ft 4 ft. I was thinking black 1mm tubing with wiring ?

Hey, can you provide some more information about what you want to do? It will help us give you a more accurate answer.
Thanks,
Anat from circuito.io