My first thought when Apple released this today was "Please be compatible with the Rode smartLav(+)" and, to my delight, it is. I'm a big fan of the smartLav for both weddings and quick interviews, but not so much for the accompanying iOS app which is horribly outdated and very buggy for me.
The Music Memos app doesn't seem to offer any kind of volume adjustment, which makes me a little nervous but my initial tests with it, using wildly varying vocal volumes, didn't show any clipping whatsoever. It might just be the perfect companion app for the smartLav. I'm going to continue testing and see if it's a viable option for use in the field.