I was excited to read of the support for AlarmDecoder, and went straight to their site. However, the latest posts on their forum by them are a year old, and the rPi Network Appliance is out of stock. Are they still in business (for real)?
Hi!
Just checked their site and noticed that they have 18 in stock 
http://www.alarmdecoder.com/catalog/product_info.php/products_id/39
Yes, I purchased a rPi one last Saturday and received it today. Currently trying to get it all set up.
Just received an AD2Pi board and attached it to a Raspberry Pi Zero W. Have not yet connected it to the Vista 21IP alarm panel. Will wait for the alarm tech coming out in a few days and let him do it. I don’t believe anything is on ID 18, but cannot be absolutely certain. Obviously, I do not want to upset the alarm system at this point. Burning the Linux image to an XD card was easy enough. Setup of the WiFi via wpa_supplicant.conf was also easy. Ser2Sock is running, but there’s no data coming in since it’s not connected to the panel.
And for some reason, the AD2Pi stopped interfacing. Despite shutdown/reboot and even removing power for some time and restoring, it’s not talking. I’m trying to re-load the firmware, but it seems to be taking an awfully long time to load 161KB of hex code. 
Some time later, after successfully re-loading the firmware to the proper serial port on the Pi Zero W, it’s happily working again. Crisis averted!! 