MakerDroid (previously Paint3d) is an app you can use to draw out a 2D shape that will then get extruded into a 3D shape, which you can then print out as a physical object using a 3D printer, or cut out of wood or other materials using a CNC router. MakerDroid was built as an educational tool to get kids excited about current technologies, like Android, 3D Printing, and CNC machines. However, it could also be a useful fabrication tool.
My pitch for MakerDroid was featured on Engadget!
Read more about the project at the House4Hack MarkerDroid page.