Coca farmers in Bolivia avoid hours of crossing steep valleys using home made zip lines (there is a video link):
http://www.notechmagazine.com/2011/07/the-flying-men-of-yungas-valley-.html
You might find No Tech magazine interesting too.
http://www.notechmagazine.com/2011/07/the-flying-men-of-yungas-valley-.html
You might find No Tech magazine interesting too.