This is a continuation of the inkscape-unicorn plugin. It allows you to draw different layers, which the 3d printer will print and put on top of each other.
This thing is very much a work in progress. I intend to parse the style properly, so I can assign differentiate between different colours and produce gcode for multi-nozzle setups, and interpret the stoke-width as a measure for the track-width. In the end it should be very much what you see on screen is what you get on the printer.
Later on I hope to be able to read gcode, transform it back to svg and have the user edit individual nodes.
A system like Doodle3D.com should also be possible, but a little more precise if you don't have to use a finger+ipad to draw.

I'll use github to further develop this thing, which I don't fully understand yet. Here is the link anyway: https://github.com/JelleB/inkscape-unicorn

the source files in the scr directory need to be copied to your inkscape extensions folder. On my computer that was C:\Program Files (x86)\Inkscape\share\extensions, ymmv.
Make a drawing and select >save as>|3D pinter gcode
It will pop up a window with some settings, change them as you please. click on and you will end with a .gcode file that can be printed on a (reprap style) 3D printer.
I used an Ultimaker to test against, which runs a recent version of marlin. If you use another firmware, you might need to modify the startup code and/or some of the actual python/gcode itself. Again, ymmv.