So I see how you can use a SmartApp Endpoint to allow an external system (such as a website I wrote to control a LiFx lightbulb) to trigger an actuator, or read the current value of a sensor. However, looking at the SmartThings documentation, I don’t see a way to trigger an external system with a SmartApp.
For example, I would like to write a SmartApp that would turn a light on when a SmartMotion sensor detects motion, and turn it off after a certain number of minutes without motion.
As it stands, I could write a polling app, but that would introduce an undesired delay into the equation.
Alternatively, if its not possible to call an external URL via a SmartApp, I can always hook it up to ifttt.com to send a twitter message, and write a php app to pull the twitter userstream, but that is just adding in 3 more layers of complexity for events to get lost in. I mean SmartMotion -> SmartHub -> SmartThings -> REST API -> LiFx is much shorter than SmartMotion -> SmartHub -> SmartThings -> Ifttt -> twitter -> twitter user stream consumer -> REST API -> LiFx.