Large touchscreen

Most of my project ideas have involved touch screens of one form or another...

Is there any way to hook up a large touchscreen to the Arduino? I have a large (18inches by 40-48inches) piece of glass that I'd love to make an interactive sign with.

Presumably the easiest way to do it would be to have a bunch of IR sensors along the sides of it, or something along those lines, but does the Arduino have enough processing capability to be able to handle input from an array of sensors like that?

The resolution wouldn't even have to be that high; even an 1" square resolution would be more than enough...

Is there an IC or coprocessor that could connect via I2C that can handle the sensor interface?

Thanks for any ideas!

You could use a webcam with finger printing software. http://www.instructables.com/id/How-to-Make-a-Cheap-Multitouch-Pad/ thats all i got. good luck