There are plenty of people who dabble in the smart-home scene who don’t have the desire to rewire switches or outlets. They’re either not comfortable doing it themselves, they don’t want to hire an electrician, or their living situation prevents it. It’s also pretty common to have dumb switched outlets that are wired to either the top or bottom socket of a switched outlet.
The idea. Have a smart outlet adapter that plugs into both sockets of a dual outlet and also itself provide two Z-Wave controllable outlets. The adapter would be able to detect a change of state in whichever of the outlets is switched at the wall and receive continuous power from the other. When the power of one of the two incoming outlets is cut, it would be able to control a configurable load (either one or both of the local outlets, or trigger a scene, etc).
Scenario: A lamp used to be plugged into a switched outlet (the bottom outlet). A smart bulb was installed into the lamp, but the user got sick of his friends turning off his smart bulb, so he plugged the lamp into the top outlet (non-switched). Given this smart adapter, he’d now have an instant 3-way toggle on the wall for his smart bulb, and regain configurable control of both of the outlets on the wall (choosing if they’re always on or switched).