At this point (September 2016) we should also mention that there are several video doorbell’s and some cameras that have their own motion sensors and can be integrated with SmartThings. Quite often these motion sensors work better outdoors than any that connect to SmartThings directly. ( One reason, to be honest, is that these tend to be more expensive devices and they can put more intelligence into the motion sensors to help filter out some of the false alarms.)
Some of these are only warranteed for indoor use, but depending on your weather may work in a sheltered location outdoors.
Current official integrations include Arlo cameras and the skybell video doorbell.
https://support.smartthings.com/hc/en-us/articles/209529506-Netgear-Arlo-Wire-Free-Camera
https://support.smartthings.com/hc/en-us/articles/211023483-SkyBell-HD-Doorbell
There also IFTTT integrations with Ring and several cameras, including blink and homeboy. Look in the “security and monitoring” channel section, not “photographs and videos” (which are for services, not devices).
And one of the community developers has a blink manufacturer approved integration with many features. You will have to pay a license fee for that one.