I suppose that depends on what you are trying to do. You can use bind_meta_app to bind certain key presses to various dialplan applications. They always begin with a *. E.g., in the default dialplan I believe *2 will turn on call recording. (Look in conf/dialplan/features.xml for some examples.)

I still don't know what the phones you have want to see in order to go off-hook automatically. Can you give us some details?
-MC