The tool is usable and it looks great, reminding us of the fun and zoomy Street Slide feature Microsoft recently introduced in Bing Maps.

One of the nifty uses for the app is zooming around one long, single page of a website. Here is an example, using the homepage of the Discovery Channel (in honor of Shark Week).

Zoom.it was created with Seadragon, the zooming technology acquired by Microsoft in 2006 that also contributed to discovery tool Pivot and 3D photo stitcher Photosynth.

Zoom.it's creators have added several features to make this tool easy, quick to use and imminently sharable. A bookmarklet lets users grab images from the Web and dump them into zoom.it without leaving their browsers, and users can use a shortcut with the address of the image, as in http://zoom.it/?url=http://readwriteweb.com, to quickly add an image. Crucially, there is a mobile version that works with touch.

Get your "pinch" technique ready. With Seadragon, you're going to have the opportunity to zoom into art, historical images, maps, NASA images, and more.

"The aim of Seadragon is nothing less than to change the way we use screens, from wall-sized displays all the way down to cell phones, so that graphics and photos are smoothly browsed, regardless of the amount of data or the bandwidth of the network."

If you've never seen Seadragon in action, I highly recommend taking a few minutes to watch a video of Blaise Aguera y Arcas demoing the Seadragon technology at TED. The technology is quite astounding - and its potential applications are even moreso. The iPhone app brings that same feeling of power - and possibility - into the palm of your hand.

But the question remains, why the iPhone? Why not some Windows Mobile device? In a word, hardware. According to Alex Daley, group product manager for Microsoft Live Labs, the iPhone has a graphics processing unit that enabled the Seadragon team to deliver an app that would have been much more difficult to build on other handsets.

While the initial app is only a demonstration of the technology, it's well worth spending some time using it. And as you're zooming into distant galaxies or considering minute details of historical documents, take a moment to appreciate how quickly it's all happening.

Seadragon Mobile is available from the App Store for free.