Like me, you probably remember the (though perhaps now somewhat vaguely) something of the launch of the original iPhone; or perhaps just taken in the the alluring brushed metal case, the mesmerising glow of it's touch screen, the promise of all that amazing functionality, the promise of magic - all before the notion of market of downloadable apps was commonplace. Though I stayed loyal to my mostly-dumb phone for a while longer, amongst the majority of my colleagues and friends it was a fairly big deal.
The iPhone, and the devices which preceeded and followed it, have undoubtedly made an impact on how how we consume and interact with information at various scales. In many cases they have changed the common paradigm of physical interaction with electronic devices, to the point where screens that won't respond to a touch or swipe cause confusion and disappointment.
There is another element of the design of the original iPhone which, though perhaps unforeseen and unplanned, has had a wide-reaching impact on design of a particular and very common peripheral: headphones. Those of you who owned a first generation iPhone might have some inkling of this if you tried to plug anything that wasn't the supplied pair of ear-buds into the handset, and found the plug it didn't fit isn't the recessed area on the top edge of the phone.
Over the following months the manufacture of accessories for the device increased, and so did the range of headphones available, each sporting a the now common place narrower barrel.
Fast forward to 2012, where the the 6.1 million original iPhones sold is dwarfed by Apple's 4s selling 4 million or so devices on launch day, or even to just under a year later in July 2008 - where find recessed headphone jack disappears from the design of the revised version of the device. Still, practically every pair of headphones you see for sale, or find bundled with a competitors device, will feature the svelt 6mm wide connector now no longer actually required.
It's a design decision with an unusual outcome that has been swept up by the popularity of the device. The impact of which has been normalise the design of huge number peripheral devices (I'd guess its in the 10s of millions) and, no doubt, one example of many.