Okay - fun answer

An implant that can be put in my head so that I can listen to music anywhere and any volume without anyone else hearing it.

You'd be able to hear the sound exactly the way you want...

No more - turn that down, I don't like that, my speakers don't sound good, your system stinks, I wanna go to sleep

I don't have to hear your music

Some might worry about mind control, but the way I see it my mind's worthless to anyone but me