In a similar type of helpfulness (though the Google one could replace this in certain cases) helm-dash is an excellent plugin. You can bring up the helm-dash menu and search your Dash docs for functions by name, or search for the symbol at point. I have mine configured to open the docs in my browser, pointing to the local docs.

If you use OS X, something is broken in browse-url (I think) which causes anchors to not get opened correctly (annoying), so I added this[0] snippet to allow it. Not robust at all, but you get the idea. The "open -a" gives window focus to Chrome, mimicking the built in behavior.

[0] https://gist.github.com/asummers/8b8dfabf0e25a86ce0c320b39ba...