My solution for doing this may be more complex than what you are looking to do, but this has worked for me to protect my garage.
I use a Raspberry Pi as an alarm server which I placed in the garage. My Pi connects to my WiFi network. I wrote a python program (let's call AlarmServer) that would run on the pI as a server task, This program would listen for an HTTP message via a ServerSocket. On the
Blue Iris PC, I wrote a python client program that would connect to the AlarmServer and send the message ALARM to the AlarmServer and then close the Socket. I configured BlueIris so that this Client program would execute when any of my cameras was triggered.
My AlarmServer program would play mp3 files via the Omxplayer program that comes with Raspian. The mp3 can be anything you wish - I recorded me saying "ALERT ALERT ALERT. YOU ARE BEING RECORDED AND POLICE HAVE BEEN DISPATCHED" to an mp3 file. I also play a police siren sound, a klaxon sound, and a whirling sound. I have cheap PC speakers connected to the Raspberry PI to produce the sound. I also have the AlarmServer program connect to the IFTTT service. Using the Maker Channel, I have IFTTT call my phone and send out an SMS message to me.
I am still trying to enhance my setup, but it does work.