The Fibaro motion sensor would be worth trying as it also detects both light and vibration. You might be able to find a place where you could put it where the siren would set off the vibration alarm. And you could get a separate trigger for the light level. It’s Z wave plus, so the range will be pretty good. And it’s quite small and battery-operated. So I think that would be the first one I would try. No wiring required, you just have to figure out the best place to stick it.
To make it work with smartthings, make sure you get the Z Wave model, not the HomeKit model.
If you are in the North American region, Homeseer has a light sensor intended to detect when the indicator light on a dumb appliance comes on or changes color. So it may also work, but it’s not available on the European frequency. It’s battery operated, so no wiring is required.
If those two don’t work, then you could try one of the various in-line devices. There’s an FAQ that lists quite a few, including the ones already mentioned:
FAQ: List of devices with dry contact input from external sources
It’s just a question of whether you’re going to be able to get enough signal out of the box to reach the next device on your network. 