I managed to stop the rigid body spazzing out when changing the lean angle by setting the angular velocity to zero, this means the bike now slides when on grass and low friction surfaces. I have removed all pitch and roll from the camera because it was making me feel dizzy, the first person ragdoll is more comfortable now.
I updated the touch input to accelerate when holding the touchpad and automatically brake when letting go, this works well and I now have a working input system that doesn't require a controller.
The track textures don't look great on the phone and I spent some time trying to fix it, anisotropic filtering didn't seem to be doing anything and I finally discovered the S6 does not support it.
I came across a Reddit post mentioning 360 degree screenshots in Unity so I found a package on the asset store and took heaps of them, I also took a lot of normal screenshots of the new assets in action.
I tried following a tutorial I found online about pairing my Wii remote with the phone but it didn't work. I'm keen to experiment with motion control on the Gear VR but the only option seems to be pairing it with the PC and sending the input over Wi-Fi like I'm doing with the Motorcycle Prototype companion app.