My car. When we traded in the older one, I insisted on getting one with all the safety bell and whistles.
This morning while out on an errand I passed the local police precinct house, and noted a motorcycle cop, kind of a tough-looking dude with a bushy beard, pulled out of the lot onto the 4-lane street I was on, and settled in behind me. I was especially aware of him, because the city recently lowered the speed limit on this road, and has threatened to tightly enforce the new limits. Eventually, he changed lanes and I lost him behind some other cars. As I passed the local high school, still on a 4-lane road, I decided to change lanes. I checked my mirror and saw nothing beside me and got ready to move over -- but the yellow warning light on the mirror flashed at me, so I kept in my lane. I then realized that the cop was beside me, in my blind spot. I had absolutely no idea he was there, and without the blind-spot warning he and I both would have had a nasty start to the day, to say the least. He slowed down and let me over in front of him.
A few blocks later I slowed down for a left turn into a parking lot, and he switched lanes and disappeared down the road.
Ironically, I had arrived at the local donut shop. I half-expected him to show up, a perfect ending to the story. But he didn't.