Eyeball tracking adjustable focus camera embedded in glasses

There are similar ideas already documented of glasses with cameras or contact lenses with cameras, but I'm adding a unique feature borrowed from DVR systems. The camera is embedded into the eye-glasses with an eyeball tracking device. The camera lens follows the eyes with some sort of mirror system and adjustable focus.

The DVR feature is that it is constantly recording into a temporary buffer. When something unexpected is happening, you probably won't have enough time to react to hit the record button, but with this system, you can watch the event unfold, then hit a button to save everything from the buffer (or some subset (i.e. save from 10 minutes ago till now)).

This would be useful for accident investigations, professional athletic game replays, teaching physical skills, etc.