"Alerting people to important sounds they cannot hear"?
(seriously I would recommend anyone to have a good browse of the accessibility features, it's several layers of user interface that most people are unaware of)
What is meant by off here? Can an app detect and do these things when the phone is fully switched off?
I built an app that listens to sounds and alerts deaf people with a flash, vibration, and notification. Emergency alerts are free (fire alarm, police siren, et). Convenience sounds like baby crying and door knock are $5/month.
Someone please be my 1st customer or tell someone deaf. Might save their life. Just wanna help people who can't hear and feed myself :)