On yeterday's show a viewer wrote in about using earphones when exercising.  The doctors all spoke abut safety issues with not hearing what's going on around you.    I have found an excellent alternative called iHeadBones.  http://www.iheadbones.com/who_osha.html.   This device transmits sound through your head bones directly into your inner ear.  It's lightweight and amazing.  Check out the website.