Producing video with your smartphone is great. Most of them can shoot full HD (even 4K), you can edit on them, and then share your video directly from the device.
Smartphone gimbals are also great. They can make your footage look cinematic and professional and take away any of the shake from your shots.
One of the best apps for smartphone shooting is FiLMic Pro -- it gives you so much manual control over focus, exposure and other settings that will make your video have that DSLR look.
The issue is that when you are using a gimbal, or even shooting hand held, it can be difficult to manipulate the manual settings in the app while shooting. The Smooth 4 gimbal from ZHIYUN, in partnership with FiLMiC Pro, aims to make it much easier to control the app all from the gimbal's handle.
The Smooth 4's features for FiLMiC Pro include mode selector to quickly switch between Reticle mode, full auto, and full manual, ability to start and stop recording and the push of a button, lock and unlock focus and exposure reticles, a side wheel to pull focus and exposure, and quick lens selection between the front facing and back facing camera. Basically the gimbal makes it so that while you are shooting in FiLMiC Pro you won't need to touch the screen, which can be difficult while you are shooting.
There's no point using FiLMiC Pro if you're not going to take full advantage of the manual settings, and there's no point using the gimbal if you're not able to use those manual settings, so the Smooth 4 is a great option for smartphone video producers.
Here's a tutorial on how it works: