What about wireless ?
There are two options:
Bluetooth and Wireless USB:
It seems Wireless USB will be easy to deal with as it will not require any changes to the code, however is expensive and you need a power source inside the keyboard.
There are no Wireless USB dongles as cheaper as bluetooth dongles are.
There are some Wireless USB Hub out there from belkin, iogear and others.
Also maybe we can find a breakout board for a wireless usb single chip like this one from wisair.
On the other side Wireless USB is not as ubiquituos as Bluetooth is, so probably if we can to support your wireless equipment (smarthone, tablet ) it should support usb and bluetooh.
However as i haven't see any market success on wusb we can consider it is a total failure or in other words: just waporware.
The only device that seems to fit in this category for the purpose of the key64 keyboard is the wisair usb dongle set, but haven't found a website to buy it.