“WiFi signals can also be exploited to recognize keystrokes. The intuition is that while typing a certain key, the hands and fingers of a user move in a unique formation and direction and thus generate a unique pattern in the time-series of Channel State Information (CSI) values, which we call CSI-waveform for that key”.
Michael Tsai – Blog – Keystroke Recognition Using Wi-Fi Signals
You have to say that at this point we need to assume that nothing is protected.