This is just a nice device now with a new IFTTT channel. Costs about $35 at Amazon. Plug in WiFi. 100 db siren. You can use different sounds for different rules. No direct integration with SmartThings, but now that it has an IFTTT channel there is good indirect integration that way. It will be cloud to cloud, though, so I wouldn’t put life and death security functions on it, but it will still fit a lot of use cases.
Remember that it will only work when power and local wifi work, and the IFTTT integration also requires Internet. So I’m thinking about it more as a doorbell chime or maybe a laundry alert or “the mail’s here” rather than security functions.
Still it’s a nice device at a good price and being able to switch between sounds on the fly is a much requested siren feature.
It also depends on the IFTTT lag at your house. Mine is generally about eight seconds, which works great for me. But I know there are people who have much worse.