Full support for precmd and preexec functionality for bash based on the zsh specification. Currently being used by bashhub.com :) More info on the client page https://github.com/rcaloras/bashhub-client
Only known limitation at this time is support for subshells. I omitted their support for now out of sluggishness and some difficulties being able to differentiate subshell commands from commands being exectued by something else in PROMPT_COMMAND or PS1