Microsoft Office Communicator Mobile for Java is an enterprise client software for Microsoft Office Communications Server 2007 R2 optimized for Java enabled cell phones. The client allows you to view colleagues availability using presence status, initiate single/multi-party IM sessions and get updated contact information from your company directory.
Get it here
Remember that you need CWA running for the Mobile Java client to work and you need to point the client to that (CWA) website and not the Edge server.
more info here