At Mobile World Congress 2012, Texas Instruments was demonstrating a stylus that communicates its distance from a tablet over ultrasonic frequencies. The tablet in this demo has a microphone in each of its four corners, which can pinpoint exactly where the stylus is pointing at the screen, even if you're not touching it. Of course, the stylus also works perfectly well along the two standard planes, but it's particularly cool when you pull back and the model correspondingly zooms out.
It's easy to imagine plenty of far-out use cases for a stylus that can positioned in 3D space. Anyone doing architectural work would have a much easier time navigating digital models, for instance. Maybe artists could start taking up digital sculpture, or maybe it could enable some Wii-style kinetic games on tablets, I don't know. At the very least businesspeople and teachers will have a great way of demonstrating and interacting with 3D objects.
The big focus of TI's presence at Mobile World Congress 2012 was their new OMAP 5-class chips, which run on Cortex A15 processors (as opposed to A9s) and is their foray into 28 nm manufacturing, but there's little new there - as far as end users are concerned, it's the same stuff as OMAP 4, only faster.
For now, this ultrasonic stylus is just a tech demo, and TI still has to get a manufacturer on the hook to actually use this product, but their spokesperson estimates that it would only take a quarter or two to see it in market once an agreement was reached. What do you guys think of this use case? After spending a healthy amount of time with the Samsung Galaxy Note, I was a little dubious about the future of the stylus, but with stuff like this showing up, it's clear that there are still a lot of unexplored use cases.