A quick glance at Vert.X suggests its just running on the JVM, so you should be able to use any Java redis client. Seems like the most common option (which is open source) is Jedis. Also, Lettuce looks popular and has the advantage of offering a non-blocking interface to redis in cases where you don't need to wait for a response.
Also, thanks for the link to the video. Vert.x looks pretty awesome.