If you've ever tried to create a work of digital art on an iPad then you may have suffered the frustration of not being able to see exactly what's going on directly beneath your finger. Even a stylus can't offer an ideal view of the exact edge of those thin outlines. Looking somewhat like it should be in the hands of a dentist, the oStylus solves this by giving tablet artists a porthole to the screen beneath. There's no need for cables or driver software, the capacitive screen for which this device was designed simply registers the flat disc at the end as though it was a human digit.

The sandblasted aluminum handle of the oStylus is held just like a pencil. At the end of the handle sits titanium wire and a hinged stainless steel disc-shaped contact. Around the underside of the disc, a vinyl film has been applied to the contact area to avoid scratching the touchscreen surface and to help give the oStylus a smooth action. Unlike a finger or stylus, the oStylus allows users to see exactly where it makes contact with the capacitive touchscreen, like that found on tablets like the iPad.

It works by conducting the body's electrostatic field through the 6.7-inch (170 mm) long and 0.23-inch (6 mm) diameter oStylus to the screen, so that the device treats it as though it's a finger. It was created by jeweler Andrew Goss for drawing and sketching on the iPad, iPhone, iPod Touch and other capacitive touchscreen devices.

The size of the disc contact has been determined after numerous prototypes indicated that the current 0.4-inch (10mm) diameter circle provides optimum functionality. Visibility would be lost with discs of a smaller diameter and there's also the danger of broken lines or worse if the touchscreen doesn't register the oStylus correctly.

The oStylus is priced at US$37.50 - although a few of the original, signed and numbered pre-production models are still available for US$75. The following video shows an early prototype in action, although some design aspects have now been tweaked the functionality is about the same: