FiLMiC Pro has been my go to app for mobile video for the past few years. Whether I want to shoot a quick personal clip or shoot some behind the scenes footage, it mostly works great. There’s one or two issues, like drifting audio and no ability to shoot 23.976fps (it does exactly 24), but it’s still the most useful video app out there.
One thing that’s a big problem common to all mobile video apps, though, is the contrast and colour typically provided by most phones sucks. The team behind FiLMiC Pro are getting around this by giving us a Log profile in future update, though. This produces an extremely flat shot out of camera, but allows for capture of more dynamic range. Filmmaker Matteo Bertoli got his hands on it early, and posted up some sample clips to YouTube.