BeanFlow, as described by James Strachan, seems like a good idea. I questioned the value of orchestration engines a while back; one of the most interesting comments was from Paul R Brown:

BPEL exists because Java, Python, Jython, and Ruby — as well as more interesting and exotic stuff like Join Java and TyCO — simply don’t support those three core aspects of the merge scenario, and doing a good implementation from scratch is complex.