The device as I'm conceiving it would be the remote link in your digital hub. Wireless and/or 2.5g/3g network capability would be essential. And as long as you've got that, plus the recording and playback capability, you've got everything you need for a phone.
The most significant thing is...
Hmmm... what is it about this device that would make the Japanese and Journalists buy this device.
The Navi-lain connection was my first thought, but that's a little weak. Lain wasn't THAT popular, although that get's my anime-lovin' blood moving. So what do the J and Js love?
Phones...