An external sensor (along the line of a Leap Motion) could track the stylus, or its movements could be recorded with onboard accelerometers and positioning sensors. There's also the chance for feedback via an LED light or a small screen on the device. And really that's about all we have to go on.

What's interesting is that one of the patent drawings shows off a bevy of devices with touch screens, including a first-gen iPod and a laptop, alongside an iPhone, iPad and a Watch. Apple might not end up releasing this -- a patent isn't a commitment to production -- but it does seem more compelling as a stylus versus just serving as an on-screen pen as it currently does.