Ah, car keys. As a fitness enthusiast -- okay, okay, an out-of-shape blob with a fitness tracker -- I can tell you that my Fitbit wristband is the ideal place to loop the basic car key. All other keys remain hidden in the car in some crevasse until Maya and I return.
This has served us well in our summer visits to nudist communities, especially since my particular flavour of band (a Flex 2) is waterproof. It's also handy for freehiking.