For cars without an LCD display in the center stack, here's a cool technology concept that doesn't work out in real life: Embed a small LCD display in your car's rear view mirror with a reflective layer over it. Most of the time, you see a normal mirror. Put the car in reverse and you see a small backup camera. How cool is that? Not very. I found it doesn't work under normal conditions. Like when the sun is shining.

I tested the mirror on a prototype 2010 Ford Fusion, a very good midsize sedan and likely the most fuel-efficient hybrid at 39 mpg city in its class (translation: Toyota Prius gets better mileage but it's smaller). At a Ford demonstration of how much the 2010 Ford Fusion is better than the 2009, I did a slalom backing exercise. With the 2009 with its smaller rear window opening, I hiked myself up in the seat, drove carefully, and didn't hit a single cone that marked the path. It took a long time, though.

Then I tried the 2010 Ford Fusion with the backup mirror and the embedded display. I shifted into reverse, looked at the backup mirror, and couldn't see the LCD display in the daytime sunlight. That's because the mirror display is small, about 2 inches, and unreadable because it's a garden variety LCD display rather than a costlier transflective display that gets brighter, not dimmer, when sunlight strikes. (As on the BMW 3 Series convertible.) So I cupped my hand over the mirror to provide shade, steered and backed with one hand, and awkwardly knocked over half the cones in my path. So much for technology.

If you think you can do better than me (you couldn't do worse), you can also buy replacement mirrors with the LCD display built in for about $225, and then buy a separate backup camera for about $100. Gentex, a big auto parts supplier, is one of the makers of the embedded LCD mirror. At night, the mirror would work just fine, as well as on cloudy days. And on the Ford Fusion it even includes a backing lane overlay marked with green-yellow-red to indicate how close you are to an object behind you.

This is another reason why every car should have an LCD display in the center stack, even if there's no navigation system.