I have written a servlet console that allows you to invoke an instance of jython inside a web container from a web browser. It is handy
to "sneak into" a running web application for trouble shooting of server side applications. It is designed for single invocation, primarily for
developers of server side applications. The jython session state resides on the server, so you can essentially close the browser and re-attach to the same session from another browser instance. Needless to say, that makes it unsafe for multiple simultaneous executions, but that should be easy to add as an option.
Check out http://vgoenka.tripod.com/jython/jython_index.html