User Interface Design
Don't be overlooked in the maelstrom of iPhone and iPad apps by forgetting the importance of design.
The prevalence of apps in Apples' App Store means its not enough to create an app, have an amazing idea and submit it to the store, someone out there will have had the idea and beaten you to it.
The defining factor of an app is going to move toward design in the next year at most.
It's fun to use, the graphics and interesting and work really well with the photography, it ticks all the design boxes.