If you are concerned about your keystrokes being broadcast wirelessly (which is a reasonable concern), I remember from a video or something I saw a long time ago that there was success in reconstructing keys pressed by the sound waves they make. Modern methods are probably better.

From what I understand Side channel attacks like that are usually theoretical in that in practice they are not very accurate, require a tremendous sample of known typed information to correlate with the recorded sounds and relies on the listening device remaining the same distance from the keyboard and the user maintaining the same verbosity of typing. Something sophisticated like that would probably be used more by a spy agency with a political or diplomatic target rather than somebody trying to steal your banking info

I'll bet sound-based skimming is even more feasible with the resurgence of mechanical keyboards (particularly among those most paranoid about these things)