I so much agree with you ! Speed of feedback is almost the only thing that matters in automated tests. I recently blog about it (http://bit.ly/2gGSvQK), but even I already used continuous testing, I had not written about it. Thanks a lot for the reminder.
Ruby Guard (https://github.com/guard/guard) seems to be an equivalent for Gulp. Concerning Java, Intellij recently added a “Run tests continuously” button in their test panel, but unfortunately, I did not manage to make it work.