The current terrain system is not suitable for mobile devices. I get a huge frame drop just by activating the terrain. Rendering seems to draw each polygon in a separate call, which is fine on PC, but kills performance on mobile. It would be great if you could use a different rendering technique on mobile. Maybe convert the terrain internally to multiple static mesh chunks.
Also the terrain shader is not optimized for mobile. Supplying a mobile friendly terrain shader would be much appreciated.