The Fotodiox smartphone gimbal is very good for its price. Documentation isn't all that great, but it's very simple to use and much less hassle to setup than other smartphone of gopro gimbals.
I used it with my iPhone 6s Plus, and it works with the apple leather case, but balances better without a case. There is no software and everything takes care of itself naturally. Fotodiox has some tips on youtube for balancing, but essentially you want to get it relatively balanced in the first place, and the motors will take care of it once you start it up. I needed to use the balancing counterweight with the 6s Plus to get it to work well enough.
Mine was missing the 18650 extension that the instructions said that it should have came with, but everything else was intact.Battery life seems to be decent, about an hour of constant use out of the 3 batteries. I vape so i had plenty of 18350 batteries laying around that are compatible with the gimbal, so battery life isn't much of an issue, and batteries for this thing are very cheap.
There really isn't much to complain about at this price point -- it's at least $50-100 less than other comparable smartphone gimbals (like the Feiyu that they sell at the Apple Store for $300), and works just as well.
I've attached some footage from this gimbal to this review so you can see how it performs. Granted, I did not take the time to balance it perfectly (which is IMPORTANT) -- and if I had one complaint about it, is that it doesn't do well in wind if it's windy outside and it tends to drift/tilt during and after pans tilts, so your shot is difficult to keep level, and it will go out of balance relatively easily, at least with a larger phone like a 6+/6S+.
It's not a 4-axis so it doesn't do great going up or down stairs, but in my experience does just fine if walking or running. If you're getting a tracking shot, operate it as you would any other gimbal and with good technique, you can get a great shot.
Ultimately, though, I returned the item and instead spent my money (more than twice as much) on the DJI Osmo. This isn't a knock on the Fotodiox product, but I needed something a little more compact and foolproof to use professionally. The Osmo gives me much more freedom in the form of accessories (and soon the X5 MFT camera allowing interchangeable lenses), but for someone just wanting to try out stabilization, the Freeflight Moto performs as well as anything else I've seen, at a more than fair price.