GPU speedups are welcome, but you don't need a shader and a gpu to insert a flashy effect.

Emacs has had this for decades: `pulse.el`. And building your own is very simple also.

You'll still need someone to write the glue code to trigger the pulse, but then a gpu patch on the backend wouldn't give you that either.

I'm sure someone on MELPA/Github has written code to do just this already.