A fascinating feature of a popular astronomy app called Star Walk is the augmented reality feature that uses a device’s camera to blend educational imagery with reality.
Star Walk is a well-known app due to its appearances in Apple ads and product release events. You might know it as the one that gives you a virtual night sky view that is controlled by the direction and angle of the iPad. Wonder what’s overhead? Point the iPad up. Wonder what’s in the sky on the other side of the earth? Just point the iPad down. Daytime? No problem. The app shows what’s there above the clouds and atmosphere. Moon behind the mountain? The app shows exactly where.
Adding to this magic-seeming technology is the app’s ability to blend the objects in the sky with what the backside camera sees. That means if you point the iPad up in the sky, the screen will show the night sky objects floating on top of what is actually visible. But rather than spend more time trying to explain this in words, here is a video showing the augmented reality app. The augmented reality part of the demo begins at 28 seconds.
[youtube]http://www.youtube.com/watch?v=stWaVqdimdw[/youtube]
The price of the Star Walk app is $2.99 which seems to me to be exceedingly low for such a powerful portable personal planetarium.  While the augmented reality aspect is stunning, the quantity of easily accessible information in the app challenges most textbooks. But when you add in the real-time nature of this app along with its man-made object database and updates, if ever you have considered writing a curriculum around an app, this would be a good one!
And for those accessory designers out there, it would be a fun challenge to make a faux telescope that viewed the iPad through the same optical telescope assembly and focusing mechanism in order to practice sighting skills inside the classroom!