Why bother buying a tablet when you can turn your monitor into one? The Duo Dynamic Digital Pen Mouse should bring up that question for most computer users, as it transforms any regular PC display into a full-featured touchscreen device.
Designed for machines running Vista or Windows 7 (it uses the tablet interface in those OS platforms), the Duo is a two-component system that makes touch response available on any computer. You can use it to navigate presentations, draw scribbles directly on the screen, mark up documents and other activities normally available strictly for tablet users.
The Duo consists of two components: a USB-connected base station that clips over the monitor and a pen that you can use as a pointer for the screen. It uses infrared and ultrasonic waves to track the pen's location at any given time, processing the movement to reflect it on the desktop. Remarkably versatile, the drawing peripheral even doubles as a regular ballpoint pen. As such, you can use it to write stuff on paper that is immediately replicated on the bundled NoteTaker software.
As of the moment, the Duo is limited to display panels that are 17 inches and below. According to Korean creator KCI Communications, they are updating it to support up to 22-inch monitors come September, with Mac availability shortly thereafter.
At a $120 retail price, the Duo Dynamic Digital Pen Mouse makes a good case for ditching the $1,000+ tablet. Unless you require the portability of one or need it for high-end rendering capabilities, this peripheral should easily handle most of the features you are likely to ask for.