A related pro-tip I learned from catering, which I now use often for leftovers, potlucks, gifts, etc. If you have things in the fridge you need to take with you when you leave your current location, put your keys in the fridge with them!

Also related: if you place anything on top of your car - coffee, wallet, briefcase - putting your keys with it makes it hard to forget & drive off.

Good idea. I know that problem myself, too, though unfortunately this solution only works with a set of vehicle keys, doesn't it?

So unfortunately not much use if you're commuting on public transport…

Or blocking the door!