xmatt: Shouldn't be too hard... as long as you're happy to dedicate a small box to running the webcam. You could use DDNS to give you an easy way to find it (unless you have a static IP where the webcam box is).

As for iOS app you'd have to find a webcam manufacturer that has one... I don't see why you couldn't just use your browser though and stream the video to it, you could perhaps set the stream resolution on the webcam so it would fit on your mobile screen without have to scroll around it.

I'd have to say though. If this is an actual security camera, or more accurately said, a camera that you and/or others would rely on for security, then you would want to make sure you have some kind of UPS etc for the box...