Is there a program that receives as input your drawing of a curve and outputs a parametric curve tracing it (reasonably close)?

Question

From what I know, B-Splines is the closest thing that we have to drawing curves and having them defined by the computer. I have some B-Spline code that does this interactively. However, those are a sequence of parametrics next to each other and they are often very cumbersome to work with. Is there anything better out there? Ideally, you'd like to be able to draw a reasonably simple curve by hand and have a program return its parametric representation, but perhaps that's too much to ask!