Modern chargers use very little power on standby, in the order of costing pennies per year. But not zero. The Asmo idea is that the charger will disconnect completely, even if still left plugged in the wall socket.

Of course, once disconnected, it cannot provide power to the phone. Rather, the phone needs to provide a little power to the charger first to switch it on. That means that a) it will not work with ever phone, only with models with OTG and possibly an appropriate "app" (ruling out Marc's own first creation) and b) it will not work if your battery is completely dead.