The RTX Dualphone 3088 is the only truly universal PC-free walkabout phone kit for either landline or VOIP calls on the market at present, and was recently reduced in price. Other similar units are available giving you the option of either a landline call or an internet broadband call, but they don't work with your Skype account because they use a different method of accessing the web.
My 2 gripes about the Danish design-studio concept of the Dualphone are:-
1) the tiny buttons and even tinier on-screen display numbers. The Siemens range has bigger buttons with clearer numbers and a better screen, but as above does NOT work with Skype and its unique algorhythms.
2) there is virtually NO after-sales support from Denmark as RTX.dk claims to be simply a design studio commissioning manufacture in Asia and they refuse to put customers in contact with the Asian factory for access to spare parts. I know this 'cos I tried to get a replacement loudspeaker from them after I'd swept my handset onto an unforgiving tiled Spanish floor whilst carelessly removing my jacket ! I had to buy a replacement handset for an exorbitant price - the Spanish agent of RTX wanted ninety euro ! But the Dualphone system is gggrrreat....and has reduced my two-monthly Telefonica bill from 100 euro to 30.