Who needs a touch screen when you can have you very own etch-a-sketch computer. Modder Martin Raynsford created this etch-a-sketch computer with some MDF and a few bottle caps. There is actually a little more involved than that, but it definitely is a cool mod.
By reusing the X and Y axis rollers, the LED and opto sensor of a trackball mouse the bottle caps can be used to move the mouse. The left and right click sensors were also places behind the bottle cap knobs.
It probably won’t get you many girls, but it will raise your geek-cred. Check out Martin’s site for a complete write up on the project.