I get the appeal. However, I don't think I'd use this much. It's bad enough watching people talking to "themselves" in public places, only to find they're using a bluetooth headset. Now, we'll watch people talking to their phones. Ugh. I'd rather type it or tap and swype to get it to do something.
An exciting feature i must admit,but i personall don't like an app that literally snatches away the joy of typing on apple's magnificent touchscreen from you and also makes you look very wierd in public places.