How to make a quick or shortcut button for smart phone using audio jack

Here is a simple method to make a quick or short cut hardware button for smart mobile phones. It uses the mic pin as input pin. If we short that pin with ground then mobile phone app can detect it as a single click and do the necessary function. In google play store search for “ iKEY” , you will find multiple free app like iKey, KeyCut, Klick, Clicky , headset droid, headset button controller etc.
This app can be used to program the short or long press, single or multiple click.
It can also be used a FM antenna if not used as mykey.
Using mic as input pin many companies has designed swipe card reader too.