Yes we have three implementations of this, and they mostly work but only some of the time :)
Problems: in a lot of dim rooms, the monitor is the main light source, and some webcams have terrible auto white balance. If you're on a Logitech camera it's totally easy, and if you're on a cheap netbook, it's awful. Still, you can solve all that, and we probably will ship a version of this soon.
That's great to know. I could probably turn the screen backlight off for a second while taking the shot. I'll play around with some shots from my camera to see how they vary. I'm looking forward to hearing more about these sorts of features!