I have a confession to make: Back in college, I acquired a disturbing habit. That is, I began to regularly lock my keys in my car by accident. I don't know if it was the stress of my coursework or some other external force that caused me to pick up this tendency (as I had never done it in high school); I only know that I ended up making a humiliating call to my mother and/or a locksmith to come to my rescue on multiple occasions as a result. However, while I may not have gotten any smarter over the years, cars apparently have.
My new car, a 2016 Ford Fusion Titanium, uses a keyless "Fob" (from the German word "Fuppe", translated as "pocket" - basically just a small IR remote) for entry and exit in lieu of a traditional key, meaning that I typically don't have to take my "key" out of my pocket during the normal course of my commute. While this has certainly reduced the risk of me locking my "key" in my car, I do occasionally find myself taking it off my keychain for some reason (usually to hand to a hotel valet or attendant at a carwash).
Now, you may presume that in these situations I would be vulnerable to the same mishaps as before, but surprisingly enough, my car has me covered. As it turns out, when I attempt to lock my car, it checks to see if the fob is still inside; in the case that it is, the car refuses to lock and honks the horn to inform me that the fob is within. While this feature may not seem like a dealmaker, it definitely bailed me out at my local Publix earlier today when I separated my fob from my keychain, dropped it in my cup holder, and later proceeded to attempt to lock my car as I was disembarking (I had just left a carwash where, as usual, I had to separate my fob from the keychain).
Needless to say, I owe the engineers at Ford a big "Thank you" for this feature; without it, I would probably be helping myself to serving of Humble Pie about right now. Sometimes, it's the smallest things that make all the difference.