If you need a wireless keyboard that works over long distances or through many walls, this might be the solution. The USB keyboard plugs into the sender board with an RFM69HCW radio. The receiver board with RFM69HCW radio plugs into the computer. All radio communications is encrypted using AES-128. Be sure to change the default encryption key in the source code.
The Arduino source code has been posted.
The README now includes more details on how the software works.