Meet the Nectro pen: a smart pen that lets you draw circuits on photo paper or a specially coated transparent film to test your ideas. It has a conductive tip and an eraser. The developers also offer magnetic components and a circuit library to complete this system.
The Nectro Pen is designed to let you bring your ideas to life, test new things, and learn a thing or two about electronics. More information is available on Kickstarter.