Taking IOS for a walk, a ride, a hike, a flight, a sky dive?
I'll be honest: I mostly use this iPhone mod'ed guitar rig while on the couch with the TV on using subtitles to follow the story. But I could be the guy that takes a walk and get's hit by a bus.
Using the Headphone port for audio input allows me to connect Battery packs
to the lightning connector for some long sessions. I could velcro the battery to guitar too or put it in my pocket.
I have a similar rig with a battery powered keyboard that has internal speakers
for playing in the garden with it on my lap. I use headphones but I could use the speakers too for a busking rig that fits in a backpack. I should look for a key tar to do the take a hike story to another controller (the iPhone guitar has Guitar to MIDI 2 installed and that's fun).