I think this could be integrated into nushell using

$env.config.hooks.pre_prompt = { mommy -1 -s $env.LAST_EXIT_CODE }

I believe this is analogous to the other integrations provided in the README, but there is a problem where it gets printed even for simply hitting enter, or clearing the screen, as it is a prompt hook.

I believe there is a way to integrate this better using display_output (which allows to mutate the output of the previous command itself, or simply print it back with mommy appended to it) and command_not_found (which is run on the occasions display_output isn't, I believe) hooks, but I'm not sure how exactly that would be implemented.