I've noticed that there's a hole inside the stylus compartment, near the mic.

It would be nice to hack some way to add a sensor there to detect the stylus presence triggering the notification led to warn that the stylus is missing.

ATTENTION: I know that it's only a crazy idea, doable only if we have some free hardware input port on the device, and excessive willpower :P . (Also, I read the fun threads about one putting GPS on stylus and swapping the LCD for LED screen, and I know how "funny" people are here )