Human current visualising sticks
It is often hard to visualise electric current because it is invisible, these sticks let you see the electric current flowing by creating a flow of lit LEDs like some christmas tree lights. They can detect the very small currents (microamps) that flow through your body when you touch both ends of an AA battery.
You can use them to show the difference between series and parallel circuits in a really visual way.
They have rechargeable batteries that can be charged with a standard micro USB cable.
A similar idea could be used in a science exhibit to make the standard electrical circuit exhibits much more intuitive, and more exciting.