I tried the following to get an Imenu composed of babel blocks, so that you
could browse/jump to blocks. But it doesn't seem to work, I'm guessing that
something about how org-mode builds the imenu-generic-expression overwrites
my entry. Is there a hook (or could there be a hook added) that allows me to
imenu-ify more constructs?

  (push (list "Source code chunks"
"^#\\+\\(source:\\|srcname:\\|function:\\) \\(.*\\)$" 2)
        imenu-generic-expression)