You are right in starting with a duplicate object with a Wireframe Modifier on it.
Baking emission in Cycles is one way, although areas with dense geometry may emit more light than you want and actually cause a glow effect like a gradient instead of a solid boundary.
You could also do this with Dynamic Paint and use the wireframe object as the "brush" and textured mesh as the "canvas". Works well, and this is documented in many places (including the Blender Manual and questions on this site).
There's another interesting method that's easy to learn, although not as obvious...
Vertex Paint + Bake Vertex Colors
Here's a cube with a Wireframe Modifier on it. Its vertices have been painted:
In case you've never experimented with this before, it's done in Vertex Paint Mode.
You can paint all vertices a single color like white, or in multiple colors as I have done in this example. You can also bake onto any color - in this example the starting texture was solid black.
Here's a UV-unwrapped cube of the same size. Its texture was created by baking the vertex colors of the wireframe cube above:
These two objects occupy the same location and overlap each other, but the screen shots were taken with only one at a time visible for the sake of showing each by itself.
This bake was done in Blender Internal with the Bake Mode set to Vertex Colors, and the 'Selected to Active' option enabled so that when you first select the wireframe object and then Shift-select the bake target object the color data gets transferred from the vertex colors of the former to the texture of the latter.