Here's a look at a few new DJI OSMO accessories, a few old ones, and how it all comes together for a nice 4K capable travel stabilizer. The Z-Axis Arm is an add-on to help smooth out any up/down jerky motions caused by walking. I feel lightweight gimbals are more prone to this movement as there is not enough mass. The Z-Axis is similar to the ISO arms you'll find on a Steadicam Vest.
The Extended Battery Adapter is a great addition if you already have DJI batteries (Phantom, Inspire1, etc) and want to shoot all day. But with the new firmware update that is supposed to give you longer run time on the stock batteries, you may not need the external battery.
The Extension Adapter will allow you to get better position for mounting some of your items. I think relocating the Phone mount behind the rear of the OSMO is a great spot and you'll be able to tilt as needed.
These are only a few items I think I would be using, but there is a number of expanded accessories available now from Bike Mounts, Car Mounts, Magic Arms, and even camera/gimbal upgrades to the new X5. Check out the DJI OSMO accessories page (here).