Rated 4 out of 5 stars
Nice and simple to use.
Too bad it's only Firefox shortcuts and not global hotkeys, but I guess you need a desktop app for it.
With bit of work you could try to make shortcuts global. https://github.com/intarstudents/keySharky/wiki/api-server
Example for Window: http://intarstudents.lv/groovesharks-global-keyboard-shortcuts-in-windows/