FOR SCREENSAVER:
* gnome-screensaver-command --poke
	* find irc channel to ask if my understanding is correct
	* file bug
	* track down bug
		* compile gnome-screensaver
* cli opt parse
	* quiet mode
		* no display window
		* no text printed to terminal
* fire up the face detector only just before going to inactive mode.
	* possibly this is how kreed's version works.  read kreed's code to find out
	* that way the camera isn't running all the time
	* maybe start 10 seconds before going inactive, then run until activity, or 10
	seconds, whichever's first.
* be more aggressive with turning off the screen.  dim the screen as soon as
it's not being looked at.  turn it off soon thereafter.
	* could be enough to save battery.  would need to power the camera sometimes,
	but would save on backlight.  need to profile.
* don't prevent sleep when face is detected, but user isn't actually looking at
screen.
	* requires pose estimation.
	* also requires estimating the direction of the eye.

OTHER IDEAS:
* authenticating a user based on face recognition (as opposed to face
detection)
	* much more difficult to do reliably
	* use object tracking and emotion estimation to require a set of facial
	expressions as authentication.
		* awesome for people who find typing hard, eg: no hands