Netflix, the kings of video streaming, just open sourced another one of their tools called "Glisten." Here's what it does:
Glisten is a Groovy library that was built to make it easier to build JVM-based applications with Amazon's Simple Workflow Services. It uses Amazon's Flow framework, but that framework by itself didn't provide some of the productivity abstractions that Netflix needed for building automation features on Asgard, which is also a Groovy/Grails application. Glisten doesn't require AspectJ or code generation.
If you're using Amazon SWF and you're a JVM shop, you might want to check this out.