This is similar to what I did ages ago with a DisplayLink device:

http://depot.javispedro.com/nit/usb/xvnc2dlusb.jpg

My approach was Xvnc and then vnc2dl which is severely outdated (on modern kernels there is udlfb). VNC is not as slow as it sounds because the target DisplayLink protocol is basically VNC on steroids.

Therefore, you can run a second X server and redirect applications on Maemo just fine.

The entire setup was very slow, but usable. I used a USB mouse.