I drive in city traffic every day. In a city with notably shitty and unpredictable drivers. Shoulder check, shoulder check, shoulder check. There's no replacement. If you have a regular mirror plus a shoulder check, what are these mirror aids adding?
Corollary: If you're changing lanes without a shoulder check, trusting just the mirror plus the sensor ... well, f**k you. That's the lazy, undisciplined behaviour standardizing these drivers aids will encourage. I'll speak for myself... when I drive cars with this mirror aid, I find myself kinda wanting to trust it enough to save a shoulder-check. I don't succumb but I see the temptation. So speaking for myself ... meh, I'm better off without the mirror aids. <old luddite rant off/>