Your comments

I don't know Coda, but this _sounds_ like what RubyMine does when it lets you jump to where a symbol (method/class/module etc) is defined with a keyboard shortcut.  Equally important, is the ability to find where a method is called from. 

CTags doesn't really work very well, and there's a plugin called SublimeCodeIntel that hasn't worked at all.  

This, plus the local history viewer are the 2 features that keep me with RubyMine.
I also second this one.  RubyMine's local history has saved me countless times.