I am driving my car and can’t pull my phone out of my pocket as it is unsafe and illegal but my Home Assistant has sent me an important notification (for example: the house is on fire or the back window has been smashed) but by the time I can get to reading it, it is too late. Instead the Home Assistant mobile app sends a TTS notifications to be sent to your phones speaker or a connected blue tooth speaker allowing you to hear the important notification at the moment it has been sent and deal with it right away.
