Trust no one, this is a motto well proven by the research done by Martin Vuagnoux and Sylvain Pasini at Security and Cryptography Laboratory - LASEC/EPFL. They managed to decode keystrokes on wired or wireless keyboards by compromising their electromagnetic emanations. Their research received Outstanding Student Paper Award! at the 18th USENIX Security Symposium 2009 in August 2009.
For a video demonstration or more information follow the link below