Sony has announced a set of smart headphones that detect body contact.  These headphones will play when they are in your ear, pause when one earbud is removed and stops the music when both earbuds are removed. 

The main drawback is that you will have to have a phone with the Sony Ericsson Fast Port.  That means that they will not work with any phone, but rather only some made by Sony.

Some additional features include an FM antenna, microphone and sound blocking.