http://www.minowireless.com/

mino wireless has a sip phone in java ME by the looks of it.
there is a freely available sip stack for java ME and looks like these guys wrote the frontend for it.
of interest is that in looking around to find this,
i found several other projects that are pretty close.
that and a comment that tmobile (my provider) is going to start banning im and sip usage.

https://sip-communicator.dev.java.ne...-communicator/
a project in development.