Raspberry Pi is a very nice hardware which can be used to solve various problems. I notice an increasing number of questions how to get access to the local PI from the internet. From a technical point of view that's not a problem: Just forward the required ports from your router to your Pi and disable on xbmc the firewall. This may cause you serious trouble because some folks from the internet will be able to access your Pi and even your local systems in your LAN. You should follow some rules in order to keep them out.

Access to your Pi from the internet is most secure if you use VPN by configuring OpenVPN on your  Pi or on your local router. That way nobody can access your local LAN without the VPN key. Another way to secure your external connections is to tunnel them with ssh. But you have to configure ssh the right way. No root access should be possible with ssh and the passwords have to be secure and contain special characters and mixed case characters. It's even better to allow access with keys only and password access is disabled.