go_robot_go

This is precisely the reason why I hate SmartThings. It makes it really easy to stick together pre-fab pieces, but the amount of work required to get it to talk to something new is ridiculous. Also be aware that this is only going to work if your ISY is exposed to the internet. The SmartThings hub only acts as a bridge between your devices and the internet. The REST call itself is going to be issued from the SmartThings cloud (not your ST hub), so if your ISY isn't reachable from the internet, SmartThings can't talk to it.