An adaptor that connects to the audio input of any smartphone. This adaptor has a microphone and a button, allowing the user to connect any headphones (your personal, expensive fancy ones) and at the same time have the feature of pausing/playing the music and answering phone calls with the button and talking on the phone with the mic.
This project is also useful if you connect your phone to your car's audio AUX input while driving.
This adaptor costs less than 2$ to make.
for more information check depotbassam's blog