That should be contained in the PhysicsNetworking extension API here:
http://captiveimagination.com/svn/public/PhysicsNetworking/trunkIt still is outdated a bit as I haven't done any work on it in a while. However, I've got a simple game that I've got nearly ready to interject networking into, but I've been sidetracked on JGN 2.0 and will most likely utilize it for a demonstration of the power of what version 2.0 provides. My time has been moderately limited recently, but I'm quickly approaching the release of JGN 2.0 and then will make some major updates to jME-Networking and PhysicsNetworking accordingly.
I will continue to support JGN 1.x so long as people are still using it though.
darkfrog