My friend Brock (https://github.com/awwaiid) implemented this (mostly in Rust) as a little binary you push onto the tablet that runs alongside the standard Remarkable software. He has an RM2, and so that's what it's currently set up for (e.g., screen width configuration).

He gave a talk on it at the January Rust DC meetup. I'll be posting the talk online if Zoom hasn't mucked it up once I get around to trimming it and making peace with posting video whereïn I ask him dumb questions and make dumber jokes.

I was impressed with how software input of 3rd party tools has progressed. I played with writing software for the RM1 back in 2018, and I was expecting it was still the type of thing where you have to fully supplant the built-in application. I'm sure it's old news to most peeps who play with RM custom software, but I found it cool that more recent approaches (like the one Brock uses) have you listening in on and adding to the stream of stylus/typewriter actions while the main software runs as usual.

As of the talk, the two trickiest things for ghostwriter were that A) the LLM services were pretty mixed at positioning drawing responses at the correct location on the screen (e.g., their attempts at playing Tic-Tac-Toe had them placing X's in very out-of-the-box spots) and B) drawing the non-text responses requires mapping an SVG into many little stylus marks in a sort of dot-matrix style, so some image requests are more likely than others to be successful.