I tried it through an HDMI splitter to two HDTV sets that works fine with my Roku box. I tried it with several devices and none worked.
1. Raspberry Pi: I could see the boot up stuff but video was cut off at the edges and I could not log in.
2. Windows7 laptop: nothing on screen no matter what I tried.
3. Samsung Chromebook.: desktop visible with video edges cut off but no log in screen in the middle, which I could see on the laptop screen. I checked display options but dual screens was not available. Also, my Logitech USB wireless mouse and keyboard did not work.
4. Motorola Droid Bionic: nothing. Are there phone options to set?
What's the point of having an HDMI port if it does not work?