I had a chance to see a presentation on CATJS in GTAC this year. I impressed by the idea. But do we have similar thing in Java or Python programming.
Answering the original question , Nothing in Java as far as I know , you probably already using test ng/spring-test so not much I can recommend . Concerning peter answer , if you have a running automation with WD / selenium - great for you!
Most chances you are still spending too much time on maintenance and can't run it on mobile web/ some browser properly (and other challenges, which some you can hear at this video GTAC 2014: CATJS: Applications That Test Themselves).
Standard isn't a magic word which solves everything. Standards are great but some times you need to think different to solve a painful problem, CATJS provide a different approach and different results.
WebDriver is an upcoming W3C standard, so if CATJS dismisses it as "we don't do WebDriver" it raises a red flag to me immediately. Is there any good reason to NOT use industry standard solutions? Cool is fine for fun, if you can abandon it and move elsewhere with ease. If we invest man-years in developing production code I prefer stable platform.
Disclosure: I never heard of CATJS before and maybe it is seriously brilliant solution - it is not obvious why, or for what.
And SauceLab can run your tests even on devices you don't own. You can rent test time.