Imagine an insuline doser inserted in patient's leg that checks constantly your blood and delivers the right amount of insuline when needed. You can recharge insuline with an injection to the doser, and you can recharge its battery by using a band that creates a magnetic field when needed. You can use this kind of doser for almost any medicament. A variant can be used to generate electric stimulus.

This can work for any kind of charger, or transformer. Using the proper circuitry the charger turns off the transformer in order to radically diminish the consumption of energy when there is no device connected to it. How many chargers do you have constantly connected to the wall waisting electricity. All chargers by law should have this capability.