Radio buttons = checkboxes with radioButtonRoot set to their parent. No need to trap anything, just set that value in the inspector.
NGUI doesn't have radial slider, but it does have a filled sprite. If you have a donut-shaped sprite, you can use a filled sprite to create a radially-filled slider just by setting the fill direction to be Radial360. The trick is having it handle dragging in a radial fashion. This is something you'd have to code.
For the arch, you can either create a 3D UI and tilt your sprites individually, or just create pre-tilted sprites to begin with.