Every time you use your phone your camera is on your face. Facial microexpressions could be automatically detected and analyzed based on the content the user was viewing at the time. This information could provide a detailed emotional picture of the individual as it relates to different stimuli.

Starbug (CCC hacker) recently found something even better.

You can use the reflection in the eye as keylogger for, say, PIN entry dialogs.

If you've already got access to the camera, would it not in many cases be trivial to have access to the keyboard?

Not when apps implement their own keyboard, for example, PayPal.