The 3Doodler is a pen that has an ink cartridge with ABS or PLA plastic, the same type of plastic that 3D printers use. When you write this in air, the plastic comes out melted, and then it will harden to form these interesting shapes that you see here. I have admit, they look hard to draw, especially when moving the pen up in the air. If you want, you can do this on paper for a puff-paints look.
This is a Kickstarter project, which means you will have to fund it to make it real. I believe that 3D printers are making quite a lot of headway and they will soon be in every home. Perhaps the 3Doodler is the thing that will really bring the age of 3-D printing to life.
I believe that you can get it on Kickstarter for $50, but it will run at $75 at launch, which will be in September of this year.