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
Certain classes of users, or any user in certain contexts, must be informed of conditions, alarms, alerts and other contextually-relevant or timebound content without reading the device screen.
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
Voice output that is requested to be presented, or the use of voice to navigate the device UI is discussed under the Voice Readback pattern.
Interaction Details
just happens, no control over the initiation at the moment it begins
but can be cancelled... think of snoozing an alarm clock: the alarm must remain in some format...
display on screen, or allow access to the text. also allow access to reading it again.
and volume must work!
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").
Use syntax that makes it clear what is being communicated...
Use a consistent voice and tone of voice, so the user can become accustomed to the reminder, and be able to comprehend the intent without listening as closely to opening phrases.
Antipatterns
Give users a moment to acclimate to the voice, even after any notification tones. Directions such as "Turn Right in 500 yards" are often not useful, as the user is still acclimating to the voice speaking through the direction statement; they may only hear "... in 500 yards." An alternative example would be "Turn coming up... turn right in 500 yards."