The BBC show Horizon investigates how exercise and mobile phone apps can give you a healthier and possibly longer life. The section from 31 to 33 minutes is particularly informative....
http://www.bbc.co.uk/iplayer/episode/b038p1pm/Horizon_20132014_Monitor_Me/
http://www.bbc.co.uk/iplayer/episode/b038p1pm/Horizon_20132014_Monitor_Me/