that wouldnt be possible, plus its stupid
1) Actually it's VERY possible
2) Its not really that stupid
You need an analog tilt sensor of some sort, ie one that works in X and Y position signals, hook it up to the X- Y- X+ Y+ points on the ds mobo and bam, tilt touch pad controller
Also you can use a tactile switch to control the pen interrupt on the touch screen microcontroller