This is the Leech Plug concept by Conor Klein, which is designed to save power. The idea is that the plug will automatically disconnect your gadget from the outlet once it’s fully charged.
it is hard to tell when electronics are or are not taking energy and many never stop taking energy if they are plugged in (e.g. cellphone chargers). this product solves that problem by using a timer circuit and electromechanics to eject its plug which disconnects your device from the wall outlet. once the plug falls out, all energy consumption stops and only resumes once the plug is inserted again.