Also, have a look at this system which uses a similar principle to make poles for antennae and tripods http://www.rolatube-expeditionary-systems.com/

This is a great concept. It inspired me to make a version with two strips of metal to strengthen against buckling. It uses hook and loop (velcro) to keep the bands connected when they're extended and each strip stores on its own drum, connected by a gear on each drum to maintain alignment. My prototype needs a curved enclosure to ensure that the metal strip extends rather than opening the winding wider. Will send a picture if I can. 

Here's the photo https://goo.gl/photos/3r8tvUTswWKw9Rc36