For example, when I create a Vine video I would like to input a clean music track. Ideally I would just hit play on Spotify and then hit record on Vine and have the track from Spotify be the background for my Vine.
I envision this as a cable that could go from my laptop to my iPhone. The audio is outputting from my laptop and inputting to my iPhone.
I don't believe such a thing exists. Maybe there is some intermediate tech I can stick in between my laptop and iPhone to serve this purpose? Something like a mixer, but hopefully significantly cheaper.