More from developer
Every time an audio jack is inserted, you will get a pop-up for setting the media volume.
This app has a service called Headset Monitor. This service runs in the background and "monitors" the headset phone jack. You have the option of setting to run this service every time the device starts.
This app comes from a personal need. I listen to music in my car by connecting the headphone output to the car audio's auxiliary input. I have to keep the media volume on the phone at a high level for the music to be audible through the car system. Later, I plug-in my headphones and nearly blow my ear drums due to the high volume!