Pretty nice, this is one of the things that I was going to experiment with a while back. It is exactly how I imagined it would look too
I have another idea that I would like to try before modding my modem with a second USB cord coming out of it. If it goes well I will not need to have a cord attached to the phone line, but I do not want to risk my only Dreamcast modem and Dreamcast console playing with it yet. Maybe in a few months when I have more cash.
Nice work let us know if you experience anything abnormal from the pi or modem with this setup. I would also like to try the wireless that another user posted but I am just not motivated lately