Is there a way to run HDMI Into my iMac and Use it as a Monitor for another device?

I'm wanting to play my Playstation®3 on my Early 2011 Model iMac. (21.5") The thing is, I can't find any devices that will let me play on my iMac threw HDMI. I can play using AV Cables in Standard Definition with a "Dazzle Recorder" or an "iGrabber/Easy Cap" but that's not going to cut it.

Recording the gameplay isn't a big deal to me, It's just It'd be so much easier If I could use my iMac as a television for my consoles. Hell, even a blu-ray player. 🙁

If there are any HDMI to USB, Or anything similar that will work, Please let me know, Price isn't a worry. If you have any way of doing this, that doesn't involve pulling anything a part, I'll be glad to hear it. 😎

I don't have a 27" iMac, Mines only 21.5"

Mini DisplayPort to HDMI - http://goo.gl/8O5i1 - Would these work, or are they output only? And how would I control the display if theres no software?