That sounds like some browser add-on, assuming you view it in a browser. If you can't find it in the add-on libraries of the common browsers (Firefox, Chrome, Opera, Internet Explorer, Safari) it's safe to assume it doesn't exist yet. But it could be a nice task to develop it.
For an application, I am looking for a software that allows the user to zoom in and scroll through (electronic pan-tilt-zoom) an incoming webcam video feed. I have found numerous softwares on the internet which allow you to modify your own outgoing webcam video (brightness, zoom, contrast etc.). But it is really hard to find one which does the same for incoming video.
Thanks in advance,