I made an extension to appease a slight reddit addiction: "What's new reddit?" https://github.com/mrspeaker/whats-new-reddit/ it highlights updates and auto-refreshes things.

I wrote it for Firefox, and then I wondered what it would take to port it to Chrome. The answer was "nothing really" - it worked out of the box for the main functionality. I had to do a small wrapper over loading settings, but having done a million extensions in the past, I was pretty surprised to see it load straight into a different browser!