MuseCam is a great iOS app for taking and editing photos. It has advanced tools like HSL and Curves, manual camera controls, and a slew of professional-looking camera presets.
The Boomerang app on Instagram turns a series of photos into a GIF-like image. However, a Boomerang and a GIF differ in one small but significant way. A video is repeated repeatedly in a GIF. In contrast, a Boomerang continuously loops a video while first playing it forward and then backward.