With the Fediverse, an emergency response app developer no longer has to ask the question, "Will people use this app?"
Even in the worst case scenario, if no one installs the app, updates will be sent through ActivityPub.
Thereafter, these updates will reach different instances -- and people will know what's happening.
The best case scenario? People will use this hypothetical emergency response app as a method to send updates to the Fediverse.