For a pet project, I am trying to fly a kite using my computer. I need to measure how far a cord extends from a device. I also need to somehow read out the results on my computer. So I need to connect this to my pc, preferably using something standard like USB.
Since the budget is very small, it would be best if I could get it out of old home appliances or build it myself.
What technology do I need to make this measurement?