I like this app for raw quality. A great help would be to have the volume control shutter release. I carry a gorilla pod tripod for impromptu occasions and when I have no other gear with me, and keeping the phone perfectly still without one is difficult.
I use the app for HDR bracketing. Having one finger adjust the exposure, and the other free to use the volume control on the earphones would be convenient and less fiddly.
If memory allowed, up to five shots rather than four would be very useful.
Displaying ISO would assist for my purposes, though not necessary.
