We've written about Rikai-esque browser extensions before, but until now, only Chrome and Firefox got the Rikai love. Safari was left out in the cold, dark night.
SafariKai is a browser extension that, just like other Rikai-tachi, gives pop-up dictionary definitions when you hover over a Japanese word. It runs smoother and looks a bit more elegant than other Rikai apps, but the dictionary definitions tend to be bulkier when compared with Rikaikun and Rikaichan.
As we've said before, these types of browser extensions can be a fine supplement to your learning, but be aware of how much you're using them. Otherwise, you'll end up reading English and not using your Japanese at all.