I have a fascination with weather and our Earth's climate, so Living Earth HD -- which simulates a live view of our planet based on real data -- is a lovely find. You can overlay weather and clock info on the gorgeous renderings of Earth, and look at real phenomena based on satellite images. There's an alarm clock and support for Retina, which makes Living Earth HD really gorgeous and functional.
In this Origin Stories, Moshen Chen, creator of Living Earth HD, talks about the problems he saw in similar products before his, and how he worked to create the app. Living Earth HD is available for the iPhone, iPad and Mac.