Applications for iPhone are generally referred as iPhone apps and are made available on iTunes store for download. Both paid and free applications are there for a vast range of user interests. People from all over the globe access these applications, view their description and select the app best fits their interest.
Thousands of apps have been developed for iPhone and iPod touch till now and more are being uploaded on Apple App stores on daily basis for iPhone, iPod touch and iPad. Many of them are rated top iPhone applications in different categories. As Apple has allowed developing apps for iPhone and iPod touch, so it’s the hottest domain in mobile application development these days.
Millions of downloads have been done so far and developers have made a lot of earning. Major categories of iPhone & iPod touch apps include News, Medical, Entertainment, Health & Fitness, Travel, Education, Sports, Business, Games, Photography, Maps and GPS.
Some application seems to be silly and frolicsome. A popular of those is named as “Steam”. Using this app, when the user blow into the microphone of iPhone, it’s blow sensor sense the blow intensity and response in form of clouds over the screen what seems to be steam.
Medical apps are such handy references which provide the user with well organized information about a number of diseases, their common symptoms and the most relevant medical procedures are also recommended. Moreover, the list of patent doctor’s hospitals and medical facilities of that very area is also provided.
“Fedex” is the outstanding example of business apps for iPhone. User can access Fedex shipping information, tracking and information about store locations. By using its GPS feature, “Fedex” show the nearest located store to user.    
iPhone hardware features have  been  blended  with ideas to shape out marvelous entertainment apps. Such a master piece is “Ocarina”, a virtual flute app, in which the user blows in the blow holes shown on screen; the microphone blow sensor converts this blow into flute sound with an acute sense of tilt added by tilt sensor.
Apple iPhone Develepor program authorizes and allow the Apple registered developers to submit finished user customized apps.
Appropriate planning and flexible design are the most crucial to cost and time.
Proper planning and design for your app is crucial to saving time and development cost. These innovations are expanding remarkably as users are being multiplied daily and so the developers.