This is very useful and nicely put together. Well done! An easy iframe embed link on the playback page would be nice (pro feature?). Also, being able to target a window using the spacebar (like the native screenshot app) would be useful, as would full screen recording (at the moment if I go to the top left of the screen with the intention of dragging the selection box over the whole screen, the menubar gets in the way). Finally, I noticed that the progress percentage goes backwards sometimes (41% ... 42% ... 43% ... 41% ... 44%)
There is a great little app for Mac and Windows called LICEcap (http://www.cockos.com/licecap/) that does exactly this. It's free and works really well. I use it all the time.
That said, this project looks awesome for when you need more fidelity than a gif and instant sharing.
Why would anyone even want this? The most important part of recording is the ability to have multiple takes, which is hindered if every take is to be uploaded at the same time. All other use cases can be covered by streaming your desktop.
Live uploading is cool. Are you sending the frames as they are being recorded & recompress on the server or do you just reserve the url upfront & upload once everything's done?