Seems pretty simple: make routines available as triggers and actions in IFTTT.
One way I’d like to use this is with Scout Alarm. When I set my alarm to Away, I’d like Smartthings to run the the “Good bye” routine to turn off my lights and lock things down. Or, when I run my “Goodnight” routine, I’d like to set my alarm to “Sleep.”
Similar things could be done with Nest.