ri-emacs has been around for a while. It hooks up Ruby’s “ri” command
to emacs so you can get the output into an emacs buffers. I’ve debugged
it for myself over the years. It seems to break easily. Right now, I
have it working for Ruby 1.9.1 on emacs 23.1 on Mac OS X.
It is on github here: GitHub - pedz/ri-emacs: Ruby ri help inside emacs
The one feature I’ve added are click-able “links” or “hot spots” in the
output. For example, if you get the ri page for the String class, each
method will be click-able. Clicking on “to_i” for example will do an
“ri” for String#to_i
Enjoy
pedz