Ok. Thanks all for replying. This can definitely be a confusing topic :).
I just want to make sure I understand everything here.
I think I need to narrow my choices to the ones that more closely match what I want and then compare and decide from those options. Here are the options I think more closely meet my needs. Please correct me if I am wrong.
I want to be able to use the existing alarm components, including keypads, just in case I need to in the future. I also do not want to replace or remove the existing alarm panel. I think this eliminates the Node and/or the ESP8266 and the Arduino methods. So I need to figure out the methods that allow me to do that. I know @redloro solution does that but it does require the software to be running/communicating 24/7. I see now there is a mention from @ritchierich, @raidflex, and @cozdabuch about using the AD2Pi device. Do these require the proxy software to run? What they do or not do that redloro’s solution does not?
Trying to figure out if these things are equal in functionality, install complexity, and requirements.