A rear-view mirror is only useful if you can see out of the back of your car -- something, it happens, that's gotten increasingly difficult to do. We pack the trunks of our SUVs and hatch-backs to the ceiling with boxes and bags, or pile kids and pets into the backseat. Sometimes even the car itself is the culprit: As rooflines in coupes and sedans slope more aggressively downward, rear windshields are being overtaken by massive blindspots.