I have checked the JS shell server code [1] onto the ZAP branch and it 
will now build by default when building ZAP.

If you append the option '-jssh' to your command line, ZAP will listen 
for telnet-like connections on port 9997 on the local loopback 
interface. Note that windows telnet doesn't work very well because of 
line-ending issues.

JSSh is very handy for debugging/inspecting/interactive development and 
for controlling aspects of ZAP that are not exposed to the UI yet (such 
as e.g. setting some codec parameters while the app is running).

JSSh works best with XEmacs, for which there is a script in 
mozilla/extensions/jssh/xemacs.
If you use XEmacs, you can install this script by placing something like 
this in your  ~/.xemacs/init.el:
 
  (setq load-path (append 
'("...path...to...zap/mozilla/extensions/jssh/xemacs/") load-path))
  (require 'moz-jssh)

Once installed you can use the function moz-jssh (CTRL-C M S) to connect 
to a running zap process.

You can then e.g. look at the current sip stack by typing something like:

var mainWin = getWindows()[0];
var sipUAStack = mainWin.SipClient.sipStack;
inspect(sipUAStack); // <- look at the sip stack through zapISipUAStack
inspect(sipUAStack.wrappedJSObject); // <- look at underlying JS object 
implementing the stack
inspect(sipUAStack.wrappedJSObject._dialogPool); // <-- shows active dialogs
...

- Alex

[1] http://www.croczilla.com/jssh