App allows user to setup a location on map with a short message, system will instantly notify the message via voice once user pass through that location if the feature turn on during driving journey.
It could be whatever message based on your creation, for instance it can be a reminder such as a message 'Passing document to Andrew' with a location setup on Andrew's house, or an alert 'Caution! speed limit 80km/h ahead' on a known Speed camera spot.