soap sessions

I'd imagine you could use Universal persistence in tandem with an XML profile. See here for info on the XML content retrieval: https://support.f5.com/kb/en-us/products/big-ip_ltm/manuals/product/ltm-implementations-11-2-0/3.html. See here for info on Universal Persistence: http://support.f5.com/kb/en-us/solutions/public/7000/300/sol7392.html.

Essentially, in a single irule you can extract a value you want to persist on from the content (in tandem with a correctly configured and applied XML profile) and then use the persist command to create the persistence record.