Free today, at least. Looks interesting. I grabbed it for my iPod Touch. Fotopedia National Parks for iPhone, iPod touch, and iPad on the iTunes App Store
Enjoy and share a daily dose of majestic scenery with these features:
★ Instant Slideshow: Transform your iPad, iPhone or iPod Touch into an endless, beautiful photo frame.
★ Search & Navigation - Explore effortlessly with Smart Tags, Smart Previews, Search boxes and Interactive Maps.
★ Wallpaper - Choose from thousands of high-resolution photos to decorate your Apple iPad, iPhone or iPod Touch.
★ Social Media - Share your favorite images via email, Facebook and Twitter.
★ Point-of-Interest Descriptions - Learn more by clicking to text descriptions.
★ Travel Planning - Keep track of destinations in Favorites.
★ Shuffle - Shake the device to travel the U.S. National Parks at random.
★ Smart Suggestions - Discover unexpected amazing vistas and keep track of your progress with the Site Counter.