I expect the tool to be able to reliably, recursively and scalably watch a directory and report events (added files, removed files, changed files) by outputting lines to stdout.
There are some examples around "hello world" level on Github:
- fsnoop prints a lot of events about everything. You can filter them;
- fanotify_watch prints events for writing files;
- fanotify-cmd - monitor just one file
- fanotify - you can specify events, but I haven't managed to get any output from it
Update: one more notable tool: fatrace.