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Whisper will give your smartphone this capability, and more.
The app is ideal for those who are not willing to miss any important messages behind the wheel of car or during a workout at the gym.
For best results use in conjunction with Google's speech synthesizer (http://goo.gl/M5RWpT).
P.S. In most cases, a bluetooth audio output during an incoming call is impossible, depending on the software and hardware features as the smartphone and of bluetooth.