How good a camera would Touch ID make? Is the Touch ID sensor good enough to deliver surveillance images (e.g. if Apple or some researcher/agency did it) ?

Would it be possible at all to get any usable imagery from the environment using only this sensor?

Maybe at least good enough to detect and distinguish gestures and motion near-field?

What is its angular/distance-specific resolution?

Scanners for example could be used as cameras in combination with advanced image processing to compensate for out-of-focus issues.
Apple states in this Apple Support article:


  The steel ring surrounding the button detects your finger and tells
  Touch ID to start reading your fingerprint. The sensor uses advanced
  capacitive touch to take a high-resolution image from small sections
  of your fingerprint from the subepidermal layers of your skin


This tells you that a) the sensor only starts reading when being touched and b) it's capacitative, limiting the typical detection distance to the sub-millimetre range (capacitance is proportional to 1/distance).