I have some musings on social games coming up, but in the meantime I got an effect even closer to what I was imagining. Again, this requires a webcam, I may try to record a version to youtube, but here it is!
Remember that if your camera isn’t showing up, you can open the settings panel to make sure it’s enabled and that it’s the right camera. On Macs especially, there are a number of cameras installed by default and it might not be auto-selecting the right one.
Also, only one program is allowed to have the webcam at a time, so you’ll have to make sure that nothing else is using it.
A little explanation: The top left is the raw video feed, the top right is the difference between the current frame and the last one.
the bottom left is an accumulation of those differences over the past ~30 frames, and the bottom right is the actual effect – try moving around to see how it works. The button in the middle lets you toggle between using the difference or the accumulated difference as the displacer.