I know it's not exactly what you're looking for, but the company I work for makes cameras that connect to iPads. Right now the camera has three lenses (Microscope, telescope, and standalone camera) that might work for what you're looking for.
Here's the website: https://exolabs.com/
And the webcam-type lens you're looking for is called the 'Variable Lens': https://exolabs.com/products/accessories.html
And right now it only works in our app (search Exo Labs in the app store) and wouldn't work with Skype, but you can still export photos and videos into your camera roll.
I apologize if me posting about my company offends anyone, I just saw the question and thought it would be helpful.