If you want it integrated with SmartThings, @geko 's Smart Alarm custom app is popular. If you read through that topic you’ll see some of the different device set-ups people are using with it.
Current Smart Alarm version is 2.4.2. Please follow this thread for updates:
Like many others, I’m interested in using SmartThings as a cheap substitute for a self-monitored alarm system. I tried using “Smart Security” app, but was not very happy with it. So I wrote “Smart Alarm” - a multi-zone virtual alarm panel. It features:
Up to 16 independent security zones
Unlimited number of sensors (contact, motion, fire, moisture) per zone
Two arming modes - Away and Stay
Optional entry and exit delays
Zones can be designated as Interior (armed in Away mode only) Exterior (armed in both Away and Stay modes) and Alert (always armed)
Zone bypass allows quickly exclude select zones
Setting of an alarm can activate sirens, turn on light switches, send push notifications and text messages
Silent …