More importantly, why don't video sites recognise this and change the aspect ratio of the player to match? Also seems like there should be some way to tag mobile video formats with accelerometer readings (and therefore orientation) during recording.

I've found Console Calculator to be quite handy in the office environment, although it is (currently) windows only. The "virtual tape", minimize-to-tray, responsiveness, and absence of the space-devouring visual number pad help are great when you're working on another business app. I will be trying gtapecalc though!
http://www.zoesoft.com/console-calculator/