Martin Vuagnoux and Sylvain Pasini of The Security and Cryptography Laboratory (LASEC) in École Polytechnique Fédérale de Lausanne, have demonstrated the vulnerability of wired keyboard to wireless interception.
The furthest interception the pair has achieved was between two rooms, through a wall of unknown construction. And, as seen int the video, decoding the signal is slow.
I suppose the next question, other than range, would be how to intercept one keyboard's output from among several simultaneously operating keyboards.
