Yamaha posted an overview video for their NoteStar app, which combines sheet music with audio tracks for practicing popular songs. This is mainly focused on the changes introduced in the 2.0 update a couple of weeks ago, but it is a good overview of the app in general... even if it is super-cheesy and done in the style of a NAMM presentation.

NoteStar is free, but songs range from $0.99, and up to $3.99 for complete band and vocal track.

Buy NoteStar on iTunes: Free