Attach the end of the cord with clear tape to the paper money or other light object.
Pull the string out to the end. Hold the round button in the centre of the disk to prevent the string from re-winding until you're ready.
Place the object where you want it. When you're ready for the surprise re-wind, Simply let go of the button in the middle and the note flies back in to your hand.
Make your own tricks by using different light objects on the end of the cord.