Apple's yearly developer conference should see iOS 8, OS X 10.10, and likely some hardware.
'Leaked' iPhone 5 Shown Booting Up to Developer Program Error Screen
The video shows the device attempting to boot but being directed to a version of the error screen that appears when activation can not be completed. Rather than linking to the iPhone developer portal, however, the text contains a placeholder string of "@@url@@".
One questionable aspect of the device is the presence of a fourth hole or window at the top front of the device that has generally not been visible from the front in previous part leaks. In the iPhone 5, the camera has been moved to above the earpiece, swapping places with the proximity sensor that moves to the left of the earpiece. This leaked device contains a small fourth hole to the left of the camera, and while previous photos showing the backside of the front panel do indeed show the window, it is has not been visible from the front in any previous leaked photos.
This leaked device also contains a rather odd-looking home button in comparison to the home button seen on the iPhone 4S placed next to it in the photos and video. Apple has tweaked the design of the home button for the iPhone 5, but the button shown in the video appears to be a somewhat poor match for the device itself.
Otherwise, identifying information on the device has been either covered up or digitally obscured, rendering any specific model number or other information impossible to read.