Multitouch gestures on the iPhone are simple and really easy to use. Mobile touch-screen devices that don't have it, however, can make Web browsing a harrowing experience. Enter Linja Zax, a new project that's trying to give users an easy way to zoom in and out of Web pages (and potentially other UI elements) with one finger only.
Similar to the "wax on, wax off" mantra of Mr. Miyagi from The Karate Kid, this simply involves moving your finger in a circular motion. Going clockwise zooms in, while counterclockwise zooms you back out. In the demo, which I've embedded at the end of the post, you can see how this would be useful to let users select from multiple pages, which would remove the need to add a dedicated on-screen button.
Technology like this and Swype is giving us less reliance on peripheral devices and making computing on devices without a mouse and keyboard a lot easier to swallow. The project has been open-sourced on Mozilla's development site. If you've got a tablet PC or touch-screen display you can add it to Firefox with the use of an extension.