After digging through the jabber material, I found that this idea already have implementation in jabber.
Here (http://www.jabber.com/media/The_Present_Value_of_Presence.pdf) is the description of Presence Only Device. Take a note on Priority =-1.
And here is another part of equation:
So what's U have? You can create an jabber account on an jabber server. Tell the XMPPGateway to update your phone presence using that account, and with priority=-1. No one can send u text msg, unless u loggin using a real jabber client.
Time to modify perl code