The jaja stylus uses sound to transmit pressure
Drawing styluses are, for the most part, simply glorified sticks. They do what your finger would do, but have a finer point. The new jaja stylus developed by Australia's Jon Atherton, however, has a few tricks up its sleeve - the big one is, it is capable of registering 1,024 levels of user-applied pressure, which it transmits to the tablet or smartphone's microphone using sound. The resulting lines drawn on the screen will be of varying thicknesses, depending on the amount of pressure applied.
The jaja has a transparent tip, so you can see the surface of the screen through it. That tip is attached to the main stylus by a ball-and-socket joint, which is in turn attached to a pressure sensor. Proprietary onboard electronics translate that pressure into high-frequency sound, which is emitted through a built-in speaker. The mic on a device such as an iPad is reportedly capable of picking up that sound, although the human ear isn't (there's no word on whether or not use of the jaja might bug any dogs in the area).
Power is supplied by a rechargeable battery, that can be charged through a USB socket on the end of the stylus. The jaja also has two buttons on its side, which can be used to switch from drawing to alternate functions, such as coloring or erasing. The stylus could also be used in non-drawing applications, with tip pressure or button-pressing being used for functions such as mouse clicks, or to move between menus.
According to Atherton, he is in the final stages of licensing the technology to a few of the "big players" in the toy and peripherals industries, and says that it may show up in products at the upcoming New York Toy Fair. In the meantime, he is raising funds for commercial development of the jaja on Kickstarter. A pledge of US$40 will get you a stylus when they're ready to go - the projected retail price is $69.95.
More information is available in his pitch video, below.