these already exist as shaders in retroarch:
https://github.com/libretro/common-shaders/tree/master/crt (see http://filthypants.blogspot.in/2015/04/more-crt-shaders.html for examples). you can view the source code for each: https://github.com/libretro/common-shaders/tree/master/crt/shaders

i think for most of these you can remove the extra passes (scanlines, blurs, etc) within retroarch shader options until you’re left with just the curvature part of the shader, but even then i think it’s going to be way too slow.

perhaps someone with opengl experience can let you know if there’s any further optimisation possible, but it seems to be a fairly basic opengl warp operation so i’m not optimistic :(