>>wicket+(OP)
Forget Linux phones for a moment, let's start with Linux PDA. As telephony part is probably the hardest to solve due to proprietary drivers and regulations, how about building tiny PDA device that does everything else except "phone stuff" - get a dumbphone for calls and SMS, maybe some will have wifi tether. And after this PDA projects grows traction, it will be time to push for telephony support.