-* 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.