Rarely do I have an idea for a smartphone app that hasn't already been done, usually 2 or 3 times with enhancements I never thought of, but I believe I had one today.
It would be "Google Street View Live" which uses the "every-20-feet" photos from GSV and displays them on your smart phone as you're driving. This is like an augmented reality app, with street names, business names, upcoming intersections etc. displayed on-screen, in real time, as you drive along the street.
Down in the corner it would show a standard Google Maps overhead view, with the route to your destination mapped out.
Meanwhile the view out the window would differ from what's on your screen only by the time of year the GSV photos were taken, and their age. Would be cool to say, "Hey, that building's new, and there used to be a tree on this corner."