Ironically - I called about the same thing yesteday. I have an application where I want to send the image on a screen to 20+ iPads in the same room. I want to be able to capture the HDMI port going into a screen and rebroadcast that to the iPad.
The information would need to be transmitted securely as it contains spreadsheets and confidential data.
This could be a whole new market for these guys. It shouldn't be difficult to modify the existing app. The corporate world would eat this up especially with the widw implementations of video in the enterprise.