Window in Window for PowerPoint against video camera feed

It would be great, especially for those following the service on-line, to be able to show PowerPoint slides (or other media) as a small window against a background of the video camera feed of the speaker.
Typically, this should take up about the top left or right quarter of the screen, leaving the rest of the screen to show the speaker. Ideally, the exact size and position of the PowerPoint window should be adjustable, perhaps as a setting.
For further consideration, it could be possible to attach this setting to one or more of the screen configurations, so that the people in the building (who can actually see the speaker) can see the PowerPoint full screen on the data projector.