This is simply an idea which has never been proven by me, and I'm curious what kind of thoughts this community might have.
We all know how CRT monitors are affected by magnets, but what we (me) don't know is how a CRT pixel's analog status might change when a magnet is present. If we could not only apply variable voltage to the pixels of a CRT screen, but also monitor the change or 'status' of each pixel as a magnet is present, perhaps we could track the movement of the magnet as it travels around the CRT screen. How is this useful? Well, for pocket PC type devices that use a plastic pen and resistance/capacitance sensors, we can completely eliminate the pressure sensor and use the pixels to track the 'magnetic point' of the pen. This would provide a lower cost solution for pen based pocket-pc's.
I know a CRT generally uses a tube to illuminate the pixels, but perhaps this can be substituted by an array of LED's. Current LCD screens in cell phones, flat screens, and portable devices do not react to magnetism in the same way that CRT's do, so I wonder if it's possible to get this effect on a small size screen.
Edit: After further researching the function of a CRT monitor, I now see that the magnetic reaction is a result of changing the magnetic signal emitted by the tube. I suppose this idea is shot now.