Can I connect the iPad 2 video out to an iMac? This is not a AirDisplay question, it's about the HDMI connection.

I don't have a TV. I use my main computer, a 27" iMac, for watching movies.

The iPad 2 has HDMI out and games can output to 1080p while using the iPad as a controller, as seen in the recent RealRacing HD announcement.

Does anybody know if it will be possible at all to use an iMac screen, and its mini display port, in place of HDMI out?
Yes you can do it using an Active HDMI to MiniDisplay port adaptor like  this  but as you can see it's not cheap