preview-auto

This package provides a minor mode `preview-auto-mode' in which the
visible portion of an AUCTeX buffer is continuously previewed.  It
can be toggled via M-x preview-auto-mode, C-c C-p C-a, or the
Preview menu.

This package works best with the following AUCTeX settings:

(setq preview-protect-point t)
(setq preview-locating-previews-message nil)
(setq preview-leave-open-previews-visible t)
(setq preview-LaTeX-command-replacements '(preview-LaTeX-disable-pdfoutput))

See README.org for further details.