Developers keep thinking up creative ways to unofficially add more functionality to the iPhone. (Is there any other way, right now?) Take Touchpad for iPhone, a just released applet essentially turns the iPhone into a wireless touchpad for a desktop, for example. According to its developer, with Touchpad for iPhone installed:

You can move the mouse around, click, double-click, and even drag (double click but keep it pressed and then move around). Vertical scrolling is even possible, by click-and-dragging on the right edge of the iPhone screen.
You can use it to control videos, show pictures, advance slides in a presentations—whatever a regular touchpad can do.

The software, which is runs on top of VNsea, a graphical VNC client—software to allow you to interact with a remote computer—for the iPhone and iPod touch, also requires Installer.app, an iPhone hack that enables you to run and intall unofficial third-party applications on your device.

Demonstration:

Article by James Alan Miller
Via PDAStreet.com