This thread will be moved as soon as I found the place where to put this...
for your question: I have a single phone at home which could do landlines and VoIP (Siemens Gigaset), it does VoIP only atm as I don't have landlines... what the N900 is capable of you know already. A land-line-number from the US, one from Germany and two direct VoIP addresses are ringing at home so far...