[twothamendment]

I'm using an AD2USB (http://www.alarmdecoder.com/catalog/product_info.php/product...) to get an old school Ademco Vista 20p hooked up to the pi. Once you do that they have a decent python project (https://github.com/nutechsoftware/alarmdecoder).

Thanks to projects like these, the old, hardwired systems can be connected and be useful for more than they were intended. I don't mind my vista 20p once it is up, but they can be pain to setup the way you want. The good news is, once you do that you likely will never touch it again.