I love the idea of added on speakers or microphones for music recording and playing. I’m a musician and would love to be able to record better sound and listen and play back (jam, if you will) without plugging in to a secondary listening device. I have a big jambox, but it’s not always ready and charged when I need it. I’ve tried apple tv airplay, but this has huge lag, and a 3.5mm to rca jack to my stereo keeps me chained to a room. It would be great to take an acoustic guitar out to the forest and record some multi track guitar parts.
It would also be cool to be able to go to a friend’s concert and record a few songs for them on your phone that didn’t sound like a rat in a tin can so they can put them on youtube.
I can see other huge benefits with this design from input DI devices to plug in a guitar or midi synth (like I can with the camera connection kit on my ipad, but better) to wide angle or macro lenses for photographers, even little selfie screens on the back so you can see what you are taking.