I wanted to make a mount mod to play games on my GS3 using a Sixaxis PS3 controller. Here are some pictures of how I made it. All parts were inexpensive and only one that is a little difficult to find was the plastic piece that I built my mount around. I bought a cheap 10 dollar or so PS3 wireless keyboard and used its mount for this. I will be using the keyboard with my old phone as a XBMC project with HDMI cord. So in the end the clip was a bonus.
You could use the USB to go feature and used a wired ps3 or xbox 360. The ps3 runs natively but the 360 requires and app available in the market. Very cool design, I bet you could sell a bunch of those.