I'm back from my trip, and getting back into Shader Shenanigans again!
Here's a simple Half Tone shader, in both an image effect variation (toggle the image effects on an off on the camera scripts) and a per object variation (the sphere in the middle).
The image effect comes in two varieties, one to override the screen colours, and one to maintain the hue and saturation, and just do the value as halftone.

There's also a "Gradient Transition" slider on the image effect shader, which I'm going to be using to transition to this effect as a background for menus, end of level score screens and the like.
As always, let me know your thoughts or if you have any problems with getting it to work. Thanks!