IFTTT lacks persistence: how do I stop the "that" later?

IFTTT doesn’t control anything – – it just passes the messages around. So it doesn’t know state, and it wouldn’t turn your Sonos off automatically because the siren is no longer on. It just gets a notice Of the original event, and passes that notice over to Sonos.

Your IFTTT applet isn’t “If the siren is on, then Play a Sonos notification.”

It’s “if the siren turns on then tell Sonos to play a notification repeatedly.”

Just set up a second IFTTT applet so that when the siren is turned off, the Sonos notification get turned off.

Or use a rules engine that does know state. :sunglasses:

How to Get Started Creating Complex Rules in SmartThings (2017) (SmartThings Classic)