The smart phone is not my favorite editing hardware platform but if you have no other choice than to edit on your phone (iPhone in this case) Filmmaker Pro does a good job. The interface resembles very much the desktop editors that you are used to work with. Even on such cramped space it manages to present you with a pretty usable timeline, with access to a file manager with all your editing assets (rushes, audio and video clips), with unlimited tracks, a good choice of effects and transitions, text and title overlays, and much more. Audio processing and voice over recording is supported by responsive audio meters. The editor handles 4K on a range of iPhones.
Very remarkable is the integrated camera with relatively easy to use manual exposure, shutter speed, ISO, focus, and white balance controls. Impressive are the video stabilizer and the possibility to use external microphones. Altogether this makes Filmmaker Pro an excellent app for the roving video maker. (iOS, in app purchases)
(image Filmmaker Pro)