I don't think you need a static IP, you just need to know your IP to connect to. If you need to know it always, you could make a small app to find your IP and upload it somewhere (your FTP space maybe?) so you can read it from anywhere on the net, and have that run as a service at home. I used this method for a game server I wrote some time ago. I wonder if you can do the same with the arduino itself and cut out the PC altogether?