Is there an app that will search the text in a message for a string and play a notification?

[AC Question]

is there an app that will search the text in a message for a string and play a notification?

I want to search incoming messages for a particular string. For example any message containing "emergency" would play a special notification tone alerting me to read it right away. The string could be contained in a message from anyone sending me the message so I can't look for a certain sender. I've looked but I can't find anything like this.

Thanks