Been working on a project to make life easier when using Plex with sonarr/radarr. Figured some of you guys may be looking for something like this.
Basically it's a webhook receiver that runs on your Plex server machine. It receives requests from sonarr/radarr telling it that a new file was downloaded. plex_autoscan will then execute the Plex command line scanner for that files directory. For me, this means new video files are available to watch in Plex within seconds, without the need to scan my entire TV/Movie library. Here's the github URL where some basic setup instructions are aswell as an explanation for what every configuration variable does.