Yes the OcamlPro ocaml-top. And I not suggest it for whole projects. The way I use it, is having at the top of the project several files named <something>_top.ml and they look something like this:
#use "topfind";;
#require "lib_1";;
#require "lib_2";;
#directory "src";;
#directory "src/util";;
#mod_use "file_1.ml";;
#mod_use "file_2.ml";;
// Some copy-paste
#show Cmdliner.Term;;
// some code which I'm trying to get right
A real example is here: ocp_indent_top.ml, I was trying to figure out how to use ocp-indent library
It is a bit tedious to set up, but the feedback which I get is quick and and yes if some definitions are changed it is reloaded if if is at beginning or middle of the file.