A domestic fire alarm that triggers on pre-ignition signatures and goes silent once there's actual smoke, and the evaluation problem that makes it unusable.
A restaurant built around a menu of paired dishes, where ordering the cautious option gets you the one you almost picked instead.
A hypothetical service that rents out stratospheric craft to cast a precise, sun-tracking shadow over your outdoor event.
A device that notifies you only about the calls people considered making to you and then abandoned — and the question of whether that number should ever be shown.