@mfalkvidd the image is based on resin.io. I will do some more digging but your advice might be the best option. I really appreciate your help on this. I will report back what I find. Thanks!

sundberg84. Thanks for the advice. The LEDs are not always a good source since they stay on after the first trigger. I was able to tap into the buzzer using an optocoupler/optoisolator. I used a simple button sketch and can get LEDs to blink on the input and output side of the optocoupler (all hardware, no software involved), as well as an LED controlled by the arduino based on input from optocoupler. The struggle I am having is getting a mysensors sketch to adopt to the gateway with this setup. I have other door switch and temp sensors in the system no problem with homeassistant. I have used the basic door/binary/button sketch with no luck. My gateway's LEDs indicate that the signal is coming through but it won't adopt. I have also tried the fire alarm sketches linked below but they will not compile even after fixing the library issue. Awesome video to learn optocouplers https://www.youtube.com/watch?v=m5UQ9nMmamo Fire alarm/mysensors tutorials that did not compile https://forum.mysensors.org/topic/934/mysensoring-a-kidde-smoke-detector-completed https://www.youtube.com/watch?v=mNsar_e8IsI Looking for ideas. I will try to post a video of my wiring and what is going on as soon as possible. I think I am just missing something simple. Thanks!