Yes, the whole phonet stack is interesting concept, looks like it allows equivalent (relatively low level) access to GSM/whatever phone module over serial (internal SSI) bus, usb or bluetooth so the phone part is either integrated or remotely connected and the tablet can serve as main interface to operate it (i.e. much more than just headset or contact exchange over bluetooth?). I wonder which existing (Nokia only?) phones support such access. I also wonder how the GPRS over phonet driver differs from GPRS over bluetooth DUN profile.

EDIT: after some investigation it looks like it is not something particularly new, gnokii already talks over it with nokia phones and Nokia currently doesn't plan to contribute more than just existing GPRS driver and internal SSI communication.