Martin Vuagnoux and Sylvain Pasini have announced study called Compromising Electromagnetic Emanations of Wired Keyboard that continues to prove that computers use electricity and things like the keyboard current can be deciphered:

Wired keyboards emit electromagnetic waves, because they contain eletronic components. These eletromagnetic radiation could reveal sensitive information such as keystrokes. Although Kuhn already tagged keyboards as risky, we did not find any experiment or evidence proving or refuting the practical feasibility to remotely eavesdrop keystrokes, especially on modern keyboards.

To determine if wired keyboards generate compromising emanations, we measured the electromagnetic radiations emitted when keys are pressed. To analyze compromising radiations, we generally use a receiver tuned on a specific frequency. However, this method may not be optimal: the signal does not contain the maximal entropy since a significant amount of information is lost.

Our approach was to acquire the signal directly from the antenna and to work on the whole captured electromagnetic spectrum.

This all reminds me of a guy in the Swedish army I once knew whose job it was to sit in a van and test the emanations from “secure” rooms. He said even a missing screw on a room surrounded by impregnable sheets of metal was all he needed to monitor keystrokes.