What country are you in? The alarm patterns are different in different countries, so the acoustic device would be different.
If you are in the US, the Leeo works well for this. It can recognize three sound patterns: a US residential fire alarm, a US residential CO alarm, or a long continuous tone such as most leak alarms give off.
Its regular price is $49, but it is often on sale for $29. You plug it into the wall and it just listens for the sound pattern. When it detects a target pattern, it then can send a Wi-Fi notification, a push notification to your phone, and it also has its own IFTTT channel, which allows for integration with SmartThings.