Hot reload for the theme preview?

Hi! Is there an easy way to add some hot reload feature to a theme preview?

At the moment my dev cycles is:

1. Making a change to a theme file.
2. Switching to the browser with the open theme preview URL
3. Hitting cmd-R, and again cmd-R, and again cmd-R - until Dropbox is synced and the server serves the new version.

Would be great if I could skip step 3 and just wait until the new version appears by itself!

I could think of some server-side injected JavaScript or maybe there exist extensions (I use Firefox) which do the same client-side?