edit: 5 minutes (and -$10) later, I now have a portable third monitor that I can bring with me anywhere in the house. Plus I can easily test my iPhone app in the simulator using real touch gestures, without building to a device (not every gesture is working, but this is still awesome).
This is basically a disguised VNC display. I test drove this app(or its clone) last year and it was noticeably laggy. Maybe things have changed since then...