Is there any way to check if a DVR recording is in progress via the API? We’re currently using /status/sessions to verify that nothing is being played before updating/restarting PMS, but it doesn’t appear to include any info about DVR recordings, so even though nothing is being played we could end up restarting PMS while you’re in the middle of recording a show which would obviously suck. 
I haven’t had a chance to verify if it is correct, but it was suggested to try /media/subscriptions/scheduled
Depending on your tuner you can hit it’s IP similar to: http://192.168.100.178/tuners.html
This will show if the tuners are being used which may help. I do this before shutting down Plex to do updates. Ideally Plex should check and warn if you try and shutdown while a recording is in process!
Carlo
I was looking for a way to do this today and wanted to comment that the below works well to get a running count of recordings.
#!/bin/bash
DATA=$(curl -sq http://127.0.0.1:32400/media/subscriptions/scheduled?X-Plex-Token=YOURTOKENHERE)
VIDEO=$(echo "$DATA" | grep '<MediaGrabOperation' | grep 'status="inprogress"'|wc -l)
echo $VIDEO