The Plex media server supports integration, including support for control during playback, database queries, and other API features.
There already is some limited support for Plex. If you enable the DLNA server in Plex, you can browse & play files on any available Media Renderer. For example, the Google Cast integration allows you browse DLNA servers like Plex & play your tracks on any Chromecast device. A more thorough integration that doesn’t use only DLNA is certainly an option if there are enough people interested.
We don’t need DLNA as we use Airplay II throughout the house and don’t have any Google devices (except for a Nest Smoke Alarm).
The kind of integration I’m hoping for is some stuff partially addressed by IFTTT, like dimming the room lights to accommodate a home theatre starting up a performance or even showing a Now Playing: screen on an Airplay screen of choice, as well as search the Plex DB by voice so you can do something like “Show me other movies by the director of this one…”. A weekly report of who watched what and when would also be a great thing to be something to implement.
I second plex integration!