The imagery comparison technique was so compelling to me that I thought I would see if I could do it in Magik. My scenario was to use imagery available via Web Maps Connector to compare imagery supplied by Bing with imagery supplied by NearMap. What I came up with was a class called a canvas_comparer. It could be used to take two snapshots of the same canvas with different contents and then easily compare the two snapshots dynamically as sliding overlays.
This video demonstrates how it works. I'm wondering if there are other temporal-type applications that this might work for. (I threw this canvas_comparer together in about 1 hour using Graham's very cool Dialog Designer. If you haven't tried the tool yet, you should!!).