This is one of the new features I thought looked really great in Apple’s upcoming OS release Mountain Lion ( http://www.apple.com/macosx/mountain-lion/features.html#airplay ) — but honestly I only see myself using that feature for videos anyway, so iTunes already does what I need. Nice.
(Still don’t get why QuickTime Player doesn’t have the same option, though. Strange… In the meantime, that’s what Air Video is for : www.inmethod.com/air-video/ Apple should really just buy Air Video and make it part of iOS as well as Mac OS. It is quite possibly the greatest app ever.)