I got it to work! Thanks to /u/shakuyi on Reddit for their help as well as ChrisRosenkreuz23 on the discord!
In the end I used the code below to have it play the RTSP stream on VLC in the background in addition to a loud notification. I also have separate commands to set the media volume and then end playback when noise is no longer detected. NOTE: This plays the audio only in the background even if the phone is locked, just as I was looking for. If you need it to pull up a video on the screen this will only get you part of the way there.
service: notify.mobile_app_<your phone>
data:
message: "command_activity"
title: "rtsp://<your RTSP stream>"
data:
channel: "org.videolan.vlc"
tag: "android.intent.action.VIEW"
Other helpful commands used in this project:
- Set Volume level for media playback (to make sure it is audible):
service: notify.mobile_app_<your phone>
data:
message: "command_volume_level"
title: 20
data:
channel: "music_stream"
- Stop playback and end VLC ongoing notification:
service: notify.mobile_app_<your phone>
data:
message: "command_media"
title: "stop"
data:
channel: "org.videolan.vlc"
- Turn on the screen so notifications are more likely to wake me up at night:
service: notify.mobile_app_<your phone>
data:
message: "command_screen_on"
- General Notification with image from the camera which will take you to correct lovelace page in the app when selected (You can also use the custom channel to have a unique notification sound accompany the stream audio in your phone’s settings)
service: notify.mobile_app_<your phone>
data:
message: Sound was detected in the Baby Room
title: Baby Crying
data:
image: >-
<your image uri as shown in Dev Tools for the camera under 'entity_picture'>
ttl: 0
priority: high
channel: baby_monitor
importance: max
actions:
- action: URI
title: Open Monitor
uri: /lovelace/baby