For users using a AVM Fritzbox and XBMC in a Windows enviroment I put together a tiny tool to display incoming Calls on the Screen of your XBMC Mediacenter.
If you put it in yor systems autostart it will automatically connects to your Fritzbox and monitoring incoming calls. As soon as a incoming call is recocnized it sends a notification Message to the Screen of your XBMC and pauses the current running Movie.