You should look up SVG (Scalable Vector Graphics). It will do exactly what you want.
Inkscape, apart from being the ultimate open-source, multiplatform, SVG editor, it can also trace images:
http://www.youtube.com/watch?v=rzmdqwFpxp8
http://www.youtube.com/watch?v=wFQ8Y386DWo
http://www.youtube.com/watch?v=r8cpJ...eature=related
You can even add numbers, text, whatever with Inkscape. All in selectable, searchable form.
For a much more accurate trace you could try Vector Magic (and edit the result using Inkscape).