Hi,
(i) As of version 10.4.1, ImageFeatureTrack uses "corners" to track positions across several images.
This is similar to https://users.cs.duke.edu/~tomasi/papers/shi/TR_93-1399_Cornell.pdf
Conceptually, the corners are detected as in ImageCorners, and tracked on successive images by best fitting the match of local regions around each corner.
(ii) Not at the moment
(iii) That's a great suggestion --- future versions of Mathematica will have tools to make such applications a bit easier. It would be nice if you could find an implementation of Active Shape Models or Snakes in Mathematica in the meanwhile. As a side note, the function ChanVeseBinarize is pretty good at fitting a contour to objects for binary segmentation.
