Considering researchers have been able to read CRTs without looking at them by Van Eck phreaking, and more recently even get LCDs (http://www.omninerd.com/news/TEMPEST_Attack_on_LCD) it's not really even game changing for a realistically secured facility. http://www.tscm.com/TSCM101tempest.html is a primer, and http://cryptome.org/nsa-tempest.htm is an in-depth guide, if you think it's worth your time and money to mitigate this kind of vulnerability.