There’re two integration paths: (1) using Alarm Server software running on a Raspberry Pi or another Linux computer, and (2) using a Zigbee bridge consisting of Arduino and SmartThings Shield. Neither is simple enough for a beginner, though.
You can read more about it in this thread:
In general, I prefer an “old school” alarm system like DSC PowerSeries over the multitude of “new age” systems like Scout, Simplisafe, iSmartAlarm, etc. because of better physical security and better expandability.
Scout and other “integrated” alarm systems can by easily disabled by the intruder by simply smashing them with a hammer before they have a chance to send an alarm (i.e. within “entry delay” interval). With DSC and other “old school” systems, smashing keypad that hangs near the door will not disable the controller that’s hidden in the closet.
The reason that “integrated” alarm systems become popular is because they’re cheaper and easier to install, but in my opinion there are less secure.