I played around prototyping a mount for an iPhone 4s. Here are a couple of pictures that might give you further ideas. I ended up finding the monitor that has been discontinued on ebay to do an implementation more like this original post when I did my restore last year. The 4" monitors do come up every now and then but I always felt an implementation of this idea with an iPod or iPhone would be really neat. The problem is the clearance for the cables. The slide in mount I was using is available at
http://www.kungl.com/ coupled with an old camera mount that swivels, and a 90 degree 30-pin connector made this interesting but I couldn't get everything to the point I liked it. With the creativity I've seen from members on the board, I bet somebody will come up with a cool implementation.