The "Download Now" link directs you to the iTunes App Store, where you must continue the download process. You must have iTunes installed in order to open the link, and you must have an active iTunes account to download the application. This download may not be available in some countries.
From Apostek Software:
An intuitive and easy to use photo and image search application that brings your favorite photos to your iPhone. Search for your favorite Celebrities, Movie Stars, Sports Moments, Personalities, Music Albums, Cartoon Strips, Funny moments, Stunts, Wildlife, Nature snapshots and more.... The Photo Sniffer provides button and touch navigation along with slide show mode that can be turned on/off by a simple shake of your iPhone. A new search leads to a thumbnail gallery of images that can be navigated upto 8 pages of photo images. Clicking the photo thumbnail launches the picture in a larger view and allows next and previous navigation. Each photo comes with a relevant caption and allows zooming in for a closer look. Slide show can be started from the thumbnail gallery page or from the image detail view. Use the 'find related images' option to do deeper searches for your favorite photos. Most excitingly, the latest application version lets you save your favorite photos to your iPhone's camera roll.