This might get marked as off topic, but I know of a variety of sites now that will output $\LaTeX$ symbols from drawing in a box, among others that will do pretty cool stuff with text.
What of piecewise functions? Does there exist a site that might output a variably-rough piecewise function from the plane by drawing on a set of axes? This probably wouldn't work for anything more than $1$ or $2$-dimensional space, but it could be pretty cool.