The iPhone is most widely used Smartphone in the USA. According to a new report by ComScore, a leading research firm, 169 million people in the U.S. use Smartphones. In other words, around 70 % of total phone users in the country are Smartphone users. Out of which, 41.9 percent are iOS based phone users. In terms of market size, iOS is far head of Microsoft, BlackBerry, and Symbian. So building an iPhone app is, of course, the best idea for businesses looking to add to the ability to market their brand. And that is why top iPhone app development services in the USA are growing fast.