don't know for sure the hw one. But mod_jk is using sessionid.
I'm not too sure about hw ones either, but a believe a lot of the newer hardware (e.g. a layer 7 switch) promises the ability to route packets based on user-specified application layer data. In the end an HTTP header is just some text in a particular point in the request stream; a SOAP header is some text in a different place. If the hw vendor promises the ability to switch based on arbitrary data, it should be configurable to handle the SOAP header.
Course, haven't bought such a piece of hw myself, so don't know from experience.