Well, setting up the consumer side (from('activemq:foo?exchangePattern=InOut')) seems to work, although my test is failing because I have a mock endpoint at the end of the route who is receiving the message almost instantaneously. This tells me that the routing slip doesn't quite work as I intended.
For the time being, I'm going to hardcode my route using the DSL, but I'd really like to work in the Routing Slip EIP for the future. --sgp