Ah right I see. So you have an existing alarm panel, it is already working with Alarm Decoder and you therefore have both the Alarm Decoder hardware and software setup.
There is a relatively simple ‘plugin’ for smarthings, it would talk to a RaspberryPi running the AlarmDecoder server, the RaspberryPi would be connected to the AD2Serial adapter.
The Smartthings ‘plugin’ consists of a device handler and a smart app. They are available here
Along with instructions.
There also seems to be a similar alternative to use an Arduino or Thing shield instead of a Raspberry Pi.
It might also be possible to link the Smartthings hub and the Vera hub using MQTT and to ‘share’ the AlarmDecoder setup from the Vera to the Smartthings.