Good point. It currently needs to be precomputed as images, so it's hard to make it customizable, but it probably makes sense to make a category of unsavory crimes. I would assume that most people dislike living near the same types of crime.
I couldn't find anything to that effect, so I wrote custom scripts. Basically, it creates an image pixel by pixel, with the pixel value corresponding to the crime density of that chunk of the map, blows it up, smooths it with a Gaussian kernel, and then uses some GIS tools to warp it and chop it up into tiles for different zoom levels.
