I've played a bit with Jetty's WebSocket support and I've found out that it should be fairly easy to integrate it with Wicket.
The ultimate goal was to create something like Ajax behavior that uses WebSocket as communication channel. The result is WebSocketBehavior which provides the ability to listen for text and binary messages sent by the client and WebSocketRequestHandler which can be used to push messages to the clients.
The integration has been extended to support Tomcat 7.0.27+.
There is also integration with Glassfish 3.1.x but there are some bugs in it and it doesn't work for now.