In my use case I also wanted to watch the pelicanconf.py file and themes directory for changes and then regenerate the output and reload the browser. Lastly I wanted to use the host/port defined in my pelicanconf.py. So I made some small edits to his script named pelican-livereload.py:
Just copy it into your Pelican top level directory and execute it:
So all you need to do is visit the SITEURL you've specified in your pelicanconf.py otherwise it defaults to http://localhost:5500. Then any edit you make causes Pelican to regenerate the files and the browser immediately refreshes. The only downside to the regular Pelican watcher feature is all files are regenerated instead of just the modified file. But for me having the browser automatically reload is is worth the extra brief delay.