Like many cars nowadays, the Mazda 6 can be equipped with a blind-spot monitoring and warning device (BSM). Using sensors, the car informs you via a little light in the mirrors (pictured) if something is in your blind spot. Should you activate the turn signal when said something is lurking, there is a loud beeping noise as a warning.

The Ford Fusion has this too and does the job of warning you of other cars should your properly placed mirrors not be sufficient or your mind wanders. The Mazda 6's system will also warn you of other cars, but it gets a FAIL because it'll also warn you of guard rails and trees and hedges and curbs and dudes 20 feet away.

When merging onto I-405 North from I-10, I signaled my intention from the right-most lane to exit onto the off-ramp ahead. The 6 loudly beeped at me (it's a bit startling) because it was picking up the guard rail and shrubs that were presently there. When I went to turn right into the garage this afternoon, BSM picked up the curb, trees, grass or previously mentioned dude even though all were actually beyond an extended right-hand turn lane placed between them and the lane I was presently in. The Ford Fusion and other systems didn't do this in the same places.

As such, I turn BSM off every time I get into the Mazda 6. And really, I'd rather have an integrated blind spot mirror, like the one found in the Ford Flex. Rather than a little light telling me there's something there, the mirror actually shows me the something that's there.