Wow! Now there is WebCam for iPad, it’s called “PhotoFast” and connected to a registered jack. PhotoFast works with all clients and makes video calling possible. Here is its presentation:
The camera has 640-by-480 pixels resolution, though, for video conferencing you will need docking station or stand, you’ll also need to find some comfortable place for a WebCam as it is quite large. But I’m sure producers will remedy this defect and release a compact version.