Martin Vuagnoux and Sylvain Pasini in an article with video have successfully capture keystrokes up to 20 meters away based on the electromagnetic signal generated by the key being depressed. The technique is fairly low tech and currently seems to be a bit slow. It involves an oscilloscope, a 1 meter antenna and code to decode the pressed keys. A formal paper is being prepared for academic review, but the video is fairly impressive.

Yet another reason never to check your bank account in a public place. Although with a range of 20 meters apartment dwellers should be wary as well.