Yep, I did similar stuff too! Used something like ntfy to push notifs to an Android or just whatever commands are available on the OS you're in (e.g., `notify-send`). And for state reads herdr has `herdr pane read` while you can happily accomplish similar results with `tmux capture-pane` or similar.
Herdr holds potential in stuff like their socket API ( https://herdr.dev/docs/socket-api/ ) and whatever enhancements they wish to bring (e.g., https://herdr.dev/docs/agent-automation/ ) so if that appeals to others, it's worth a shot.
But for most regular users, tmux and other multiplexers work just fine.