Winswitch is like 'screen for X11', in that it allows you to start an application on a remote host, connect to it remotely, disconnect, and re-connect later and everything will be as you left it. It decouples the viewing of a graphical application from the running of it.
You can achieve a similar effect with X11 forwarding in ssh, by using ssh -Y <hostname> <application>
, but when you disconnect the application will quit.
The connection itself is made with Xpra, which is like VNC but allows more efficient video and audio compression.