I created something like this a long time ago (about 2 years, in fact) in the now defunct tryrethink.info[1]
I worked on it some more after doing a few try* sites, and open sourced a version [2] which could take any docker image name and do the same.
1: https://blog.docker.com/2013/07/try-rethinkdb-in-the-cloud-w...