The whole retro phone thing started back in 2004 with the Pokia. I just saw one of these handsets in a gift shop the other day offered for a couple dollars. ThinkGeek offers now a 'usable' version of the retro handsets that does not need wires. It works via Bluetooth.
This is apparently an original ThinkGeek design and is not sold anywhere else. There are though other Bluetooth retro handsets available. For example UK based Hulger offers the Penelope for $175.
The ThinkGeek Bluetooth Retro Handset sells for only $39.99.
More ThinkGeek Gadgets.