Capturing movement importance - logistic regression output
You can calculate a distance in Euclidean space. 

Given your specific goal, you can define a custom distance metric that would the equivalent of a hinge loss. For the most of the space, distance is not defined because the probabilities can be thresholded to zero. For a small section of space near (100, 50), there is a linear or nonlinear distance defined.

An alternative is to switch classifier to a support vector machine (SVM) with a hinge loss which would more directly model your problem.