I wish my phone could be listening to me all the time, and search for things I say like "when was Mozart born". I'm not sure how it would get the answers back

I wish my phone could be listening to me all the time, and search for things I say like "when was Mozart born". I'm not sure how it would get the answers back to me. Maybe an ear-piece? I think that would be the ultimate mobile search. Has anyone tried making an app like that? Can an app on the iPhone or Android access an ear-piece?