Another experiment I wanted to do and I finally found the time to work my way through this.
You can download the file here :
The effect is activated by a proximity empty object, the file is setup for a plane but you can apply the same technic on any kind of surface.
The limitation will be the memory for rendering, millions and millions of points are now less memory expensive since blender added the point cloud feature but still, it will always requires a bit of memory.
I am happy to share this with you, please feel free to ask your questions in a comment, I’ll do my best to answer.