Greg Christie the senior software engineer of Apple in an interview with the wall street journal revealed how the first iPhone came to be. Christie was a member of the team who worked on the device back in 2005. According to the interview, while the team was trying to brainstorm on how the device should look like, the then CEO, Steve Jobs gave them an Ultimatum of 2 weeks to deliver. This brought about the earliest concept for the iPhone, which was envisioned as a mix between a touch-screen phone and an iPod, without a physical keyboard.
Christie is credited with a patent for iPhone's "slide to unlock" feature and he describes the original team behind the iPhone as "shockingly small."
Other highlights from the interview include Steve Jobs' determination to keep the project a secret, which included having employees encrypt early images of the iPhone, as well as his obsession with details, including stepping in and changing the email view on the iPhone right before launch.