Apple’s iPod touch has come a long way since its debut in 2007, a year that saw the company take pains to describe the device as a stripped-down iPhone—the Wi-Fi-only touch was “training wheels” for Apple’s flagship product, as the company’s CEO once put it. The first-generation iPod touch was thinner and simpler than an iPhone, but lacked for enough hardware and software that customers were supposed to covet the…