Are there any application which lets me play the music in my iPhone through the USB cable?
It will be very convenient if I can just dock the phone (while the music is playing), and the music will come out from the computer's speakers instead of the speaker in the iPhone.
Stock iPhone dock does have a line-out jack, thanks SidneySM for reminding me.
Now the problem is, even though I have select Line In as the Sound Input in Mac OSX, there is no sound coming out from the speaker. How do I make the Speaker output the Line In audio?