Has anyone used it or gotten good with it? I have found very little online.
The QMK approach is a little more mature from what I can tell. The acceleration keys seem nice.
what is it?
Mouse emulation is when you can move the mouse using keyboard keys.
Popular keyboard firmware allows it:
Oh and the warp keys here have a similar design: https://kaleidoscope.readthedocs.io/en/stable/plugins/Kaleidoscope-MouseKeys.html
This too: https://github.com/rvaiya/warpd