There's also Hyperion. You can do something similar (via screen capture). Here's a Pi running Kodi with Hyperion in the background. There's an Arduino connected over usb to the Pi collecting serial data and sending pixel data via PWM. https://m.youtube.com/watch?v=nXGoJT2Xdk0 Not nearly as soon as OP but it's a really cheap way to get into it.
Compared to solutions intercepting HDMI output, such solutions have the advantage to only use the original video as input, without the subtitles or the user interface.
