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.
Try CMD+R... Just discovered this. It's much better than that plain code navigator IMHO :-)