I just got a new PHS300, powered it up, plugged in my TM506 via usb cable, and woala! Without any editing of settings on my phone, I'm on the internet on my iPod Touch via Wifi (of course after initial login to phs300 own's login webpage).
This can't be simpler, and I wonder why TM506 is not listed as a compatible phone. I think someone on this thread from Cradlepoint even said there have not added any support for Sony Ericsson phones. I was EXTREMELY skeptical at first as there were no testimonial about PHS300 and TM506 on the net, but what an extreme opposite the experience has been.
I wanted to add this so others know that I did have very QUICK and GOOD success with PHS300 and TM506.