Voice reads out without warning. "Time to go to the dentist." Privacy concerns,
Think about GPS directions, and how much its become a joke. Make it better!
Alison's phone announces (badly!) callers with a text-to-voice. Use that as a good sample where it sorta crosses with reminders (it's a notification, with privacy etc. issues) as well as on onscreen readout, but also as an anti-pattern since it launches into it, and is un-understandable).
Needs to probably be after you ack that a message has arrived, so are paying attention, but a valid method for low-vision, or otherwise cog disabled folks. We designed these for PillPhone, so have some of it, but do be prepared to tell me if it's not to the level of pattern, and is wishful thinking.
Problem
Solution
... the screen may be available to display other content, or able to be glanced at to retrieve certain types of data, but not such that text can be read easily or safely. The use of Voice Readback allows display
Variations
In context - like turn by turn directions
Change of context - Alerts, out of the blue
Interaction Details
Presentation Details
"Uh..." equivalent, such as a tone, to make user aware the device is going to make a sound, and so on... look it up...
and "uh" acclimation issues (look up research, people understand each other due to a tone/volume/accent level setting by our "uh's").
Antipatterns