This normal looking AC power supply is really a complete hidden camera system.
It plugs into any wall outlet just like you would expect. When plugged in, it automatically records hidden video to the included SD card. To playback footage, you can connect the unit to your computer's USB port or connect the memory card to your computer.
It comes preprogrammed for your convenience so there is no setup. You are up and running right out of the box.
Learn more about it here